DS1615K - Maxim Integrated

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FEATURES

 Digital thermometer measures temperature

-40°C to +85°C in 0.5°C increments (-40°F

to +183.2°F in 0.9°F increments)

 Digital thermometer provides ±2°C accuracy

 Real Time Clock/Calendar in BCD format

counts seconds, minutes, hours, date, month,

day of the week, and year with leap year

compensation (Y2K compatible)

 Automatically wakes up and measures

temperature at user-programmable intervals

from 1 to 255 minutes

 Logs up to 2048 consecutive temperature

measurements in read-only nonvolatile

memory

 Records long-term temperature histogram in

63 bins with 2.0°C resolution

 Programmable temperature-high and

temperature-low alarm trip points

 Two serial interface options: synchronous and

 asynchronous

- 3-wire synchronous serial interface

- Asynchronous serial interface compatible

with standard UARTs

 Memory partitioned into 32-byte pages for

packetizing data

 On-chip 16-bit CRC generator to safeguard

data read operations in asynchronous

communications mode

 Unique, factory lasered and tested 64-bit

serial number

ORDERING INFORMATION

DS1615 16-Pin DIP

DS1615S 16-Pin SOIC

PIN ASSIGNMENT

Package Dimension Information can be found at:

http://www.dalsemi.com/datasheets/mechdwg.html

PIN DESCRIPTION

Vbat - Battery Supply

X1 - Crystal Input

X2 - Crystal Output

NC - No Connect

INSPEC - In-specification Output

OUTSPEC - Out-of-specification Output

INT - Interrupt Output

GND - Ground

ST - Start/Status Input

RST - 3-wire Reset Input

I/O - 3-wire Input/Output

SCLK - 3-wire Clock Input

TX - Transmit Output

RX - Receive Input

COMSEL - Communication Select

VCC - +5V Supply

DS1615

Temperature Recorde

www.dalsemi.com

VCC

COMSEL

SCLK

I/O

RST

VBAT

INSPEC

OUTSPEC

INT

GND

DS1615 16-Pin DIP (300 mil)

DS1615S 16-Pin SOIC (300 mil)

View

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DESCRIPTION

The DS1615 is an integrated temperature recorder that combines a real time clock with temperature data

logging and histogram capabilities. It has been designed for applications that require temperature

profiling over a given period of time. A programmable sampling rate feature makes the device ideal for

applications requiring temperature monitoring over short or long time frames. The integrated Real Time

Clock (RTC) provides seconds, minutes, hours, day, date, month, and year information with leap year

compensation and also provides an alarm interrupt. Temperature measurement is provided via integrated

thermal technology which can measure temperatures from -40°C to +85°C in 0.5°C increments.

The DS1615 is a powerful data recording device, providing both a datalog of sampled temperature values

over time and a histogram of temperature. The datalog function samples the temperature at a user defined

sample rate and writes the data to the Temperature Datalog memory. Up to 2048 datalog samples may be

recorded. Histogram functionality is implemented by sampling the temperature and then incrementing

the count value in a data bin associated with that temperature. The DS1615 provides 63, 2-byte data bins

in 2°C increments. The user can program data sampling for both data logging and for histogram

tabulation at intervals ranging from once per minute to once every 255 minutes.

The DS1615 also supports programmable high and low temperature alarm trip points that allow the

device to monitor whether the temperature stays within desired limits. The device can drive an interrupt

or status pin if the temperature falls outside of the programmable limits. The DS1615 can be

programmed to begin sampling data via a pushbutton input or via a command sent over the serial

interface with a host machine.

The DS1615 also provides a 64-bit serial number, which is useful for product identification and tracking.

OVERVIEW

The block diagram in Figure 1 shows the relationship between the major control and memory sections of

the DS1615. The device has five major data components: 1) Real Time Clock and control block,

2) 32-byte User NV RAM with 64-bit lasered serial number, 3) 96 bytes of Alarm event/duration

memory, 4) 128 bytes of histogram RAM, and 5) 2048 bytes of datalog memory. All memory is arranged

in a single linear address space.

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DS1615 BLOCK DIAGRAM Figure 1

SIGNAL DESCRIPTIONS

The following paragraphs describe the function of each pin.

VCC- VCC is a +5-volts input supply. Communication with the DS1615 can take place only when VCC is

connected to a +5-volts supply.

Vbat- Battery input for standard lithium cell or other energy source. All functions of the DS1615 with the

exception of the serial interface circuitry are powered by Vbat when VCC< Vbat. All functions are powered

by VCC when VCC > Vbat. If a battery or other energy source is not used the Vbat pin should be connected

directly to GND.

GND - Ground

COMSEL (Communication Select Input) - This pin determines whether serial communication is

asynchronous or synchronous. When pulled high to VCC, communication is synchronous and will take

place via the SCLK, I/O, and RST pins. When COMSEL is tied to ground, asynchronous communication

utilizing the TX and RX pins is selected. If this pin is floated, the DS1615 will operate in the

asynchronous communications mode since the COMSEL pin has a weak internal pulldown resistor.

Tx (Transmit Output) - Transmit output of the asynchronous serial interface. Tx is tri-stated whenever

VCC < Vbat.

Rx (Receive Input) - Receive input of the asynchronous serial interface.

SCLK (3-wire Serial Clock Input) - The SCLK pin is the serial clock input for the 3-wire synchronous

communications channel.

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I/O (3-wire Input/Output) - The I/O pin is the data Input/Output signal for the 3-wire synchronous

communications channel.

RST (3-wire Reset Input) - The RST pin is the communications reset pin for the 3-wire synchronous

communications channel.

INT (Interrupt Output) - The INT pin is an open drain active low output that can be connected to an

interrupt input of a microprocessor. The INT output remains low as long as the status bit causing the

interrupt is present and the corresponding interrupt-enable bit is set.

INSPEC (Open Drain In-Specification Output) - This pin, in conjunction with the OUTSPEC pin, is

used to signal the status of the operation and data of the DS1615.

OUTSPEC (Open Drain Out-of-Specification Out-put) - This pin, in conjunction with the INSPEC pin,

is used to signal the status of the operation and data of the DS1615.

ST (Start/Status Button Input) - The ST pin provides two functions. First, when enabled as the datalog

start source (SE bit in Control register is a logic 1), the ST pin is used to instruct the DS1615 to begin

recording temperature data based on the programmed start delay and data sample rate. The ST pin must

be held low for at least 0.5 seconds for a datalog mission to begin. An external pullup resistor should be

connected to this pin.

Secondly, the ST pin can be used to poll the status of the recorded data. After datalogging has begun, the

ST pin instructs the DS1615 to report the status of the recorded data via the INSPEC and OUTSPEC pins.

X1, X2 - Connections for a standard 32.768 kHz quartz crystal, Daiwa part number DT-26S or

equivalent. For greatest accuracy, the DS1615 must be used with a crystal that has a specified load

capacitance of 6 pF. There is no need for external capacitors or resistors. Note: X1 and X2 are very high

impedance nodes. It is recommended that they and the crystal be guard-ringed with ground and that high

frequency signals be kept away from the crystal area. For more information on crystal selection and

crystal layout considerations, please consult Application Note 58, Crystal Considerations with Dallas

Real Time Clocks.

NC (No Connect) - This pin should be left unconnected.

MEMORY

The memory map in Figure 2a shows the general organization of the DS1615. As can be seen in the

figure, the device is segmented into 32 byte pages. Pages 0 and 1 contain the Real Time Clock and

Control registers (see Figure 2b for more detail). The User NV RAM resides in page 2. Pages 17 to 19

are assigned to storing the alarm time stamps and durations. The temperature histogram bins begin at

page 64 and use up four pages. The temperature logging memory covers pages 128 to 191. Memory

pages 1, 3 to 16, 20 to 63, 68 to 127, and 192 and up are reserved for future extensions.

The end user can write only to the Real Time Clock and Control registers and the User NV RAM. The

rest of the memory map is read-only from the end users perspective.

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DS1615 MEMORY MAP Figure 2a

Address Register Definition Page(s)

0000H

001FH RTC AND CONTROL REGISTERS 0

0020H

003FH (RESERVED) 1

0040H

005FH USER NV RAM 2

0060H

0217H (RESERVED FOR FUTURE EXTENSIONS) 3 – 16*

0218H

021FH SERIAL NUMBER 16**

0220H

027FH ALARM TIME STAMPS AND DURATIONS 17 - 19

0280H

07FFH (RESERVED FOR FUTURE EXTENSIONS) 20 - 63

0800H

087FH TEMPERATURE HISTOGRAM (63 BINS OF 2 BYTES EACH) 64 - 67

0880H

0FFFH (RESERVED FOR FUTURE EXTENSIONS) 68 - 127

1000H

17FFH TEMPERATURE DATALOG MEMORY (64 PAGES) 128 - 191

≥1800H (RESERVED FOR FUTURE EXTENSIONS) 192 +

* First 8 bytes

** Last 8 bytes

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DS1615 RTC AND CONTROL PAGE Figure 2b

ADDRESS BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 FUNCTION

00 0 10 Seconds Single Seconds

01 0 10 Minutes Single Minutes

1002 0 12/24

A/P

10 h Single Hours

03 0 0 0 0 0 Day Of Week

04 0 0 10 Date Single Date

05 0 0 0 10 m. Single Month

06 10 Years Single Years

Real Time Clock

Registers

07 MS 10 Seconds Alarm Single Seconds Alarm

08 MM 10 Minutes Alarm Single Minutes Alarm

10 h09 MH 12/24

A/P

10 h

alm

Single Hours Alarm

0A MD 0 0 0 0 Day Of Week Alarm

Real Time Alarm

Clock

0B Low Temperature Threshold

0C High Temperature Threshold

Temperature

Alarm

0D Number Of Minutes Between Temperature Conversions Sample Rate

0E EOSC CLR 0 SE RO TLIE THIE AIE Control

0F (reads 00h) Reserved

10 (reads 00h) Reserved

11 Current Temperature Temperature

12 Start Delay Register (LSB) Start Delay

13 Start Delay Register (MSB) Start Delay

14 TR MEM

CLR

MIP SIP LOBAT TLF THF ALMF Status

15 Minutes

16 Hours

17 Date

18 Month

19 Year

Start Time Stamp

1A Low Byte

1B Medium Byte

1C High Byte

Current Samples

Counter

1D Low Byte

1E Medium Byte

1F High Byte

Total Samples

Counter

20-3F (Read 00H) Reserved

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DS1615 ALARM TIME STAMPS AND DURATIONS Figure 2c

Sample Counter Address

(Low, Medium, High Bytes)

Duration

Address

220, 221, 222 223 T1 Low

224, 225, 226 227 T2 Low

228, 229, 22A 22B T3 Low

22C, 22D, 22E 22F T4 Low

230, 231, 232 233 T5 Low

234, 235, 236 237 T6 Low

238, 239, 23A 23B T7 Low

23C, 23D, 23E 23F T8 Low

240, 241, 242 243 T9 Low

244, 245, 246 247 T10 Low

248, 249, 24A 24B T11 Low

24C, 24D, 243 24F T12 Low

250, 251, 252 253 T1 High

254, 255, 256 257 T2 High

258, 259, 25A 25B T3 High

25C, 25D, 25E 25F T4 High

260, 261, 262 263 T5 High

264, 265, 266 267 T6 High

268, 269, 26A 26B T7 High

26C, 26D, 26E 26F T8 High

270, 271, 272 273 T9 High

274, 275, 276 277 T10 High

278, 279, 27A 27B T11 High

27C, 27D, 27E 27F T12 High

DS1615 HISTOGRAM MEMORY Figure 2d

Address (Low – High Byte) Register

800 – 801 -40, -39.5, -39, -38.5°C Data Bin

802 – 803 -38, -37.5, -37, -36.5°C Data Bin

804

↓

87B

↓

87C – 87D 84, 84.5, 85°C Data Bin

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THERMAL SENSOR

The key to temperature monitoring in the DS1615 is an integrated thermal sensor. The thermal sensor

can measure temperature from -40°C to +85°C in 0.5°C increments (Fahrenheit equivalent is -40°F to

+183.2°F in 0.9°F increments). The thermal sensor provides an accuracy of ±2°C.

The format of temperature data is defined such that the temperature value is maintained in a single byte of

data. Table 1 illustrates the format of the temperature data byte format. The values of T[7..0] range from

00000000b (for -40°C) to 11111010b (for 85°C). Each increment in the value of T[7..0] represents an

increase in temperature of 0.5°C. The following formula can be used to translate the temperature data

byte value into degrees Celsius: °C = 0.5(T[7..0]) - 40

TEMPERATURE DATA BYTE FORMAT Table 1

MSb LSb

T7 T6 T5 T4 T3 T2 T1 T0

When a datalog mission has been initiated, the DS1615 provides temperature recording at regular

intervals. However, the device also allows for immediate temperature sensing upon a users command

when the device is not currently on a datalog mission. This is accomplished by issuing the Read

Temperature command to the DS1615 over the serial interface.

The most recently recorded temperature value is written to the Current Temperature register, regardless of

whether that value was recorded from a datalog mission or from the issuance of the Read Temperature

command. The status of the contents of this register is provided by the Temperature Ready (TR) bit in

the Status register. If TR is a logic 1, the data is valid. If TR is a logic 0, the data may not be reliable.

During a datalog mission, the TR bit is cleared to a logic 0 when a temperature conversion has been

initiated and is set to a logic 1 upon the completion of the conversion. Likewise, the TR bit is cleared

immediately after the Read Temperature command is issued and is set to a logic 1 upon the completion of

the conversion.

DATA LOGGING

When the DS1615 datalogging function is enabled, the device is said to be on a datalog mission until the

data-logging is stopped.

During a datalog mission, temperature samples are successively written to the Temperature Datalog

memory pages. These memory pages are located at addresses 1000h to 17FFh. The first sample is

written to address location 1000h. The second sample is written to address location 1001h. Likewise, the

address is incremented with each additional data sample. A total of 2048 registers have been reserved for

datalog data.

A datalog mission can be initiated via two different methods; by a host instruction over the serial

interface or by a pushbutton input. When the SE bit in the Control register is cleared to a logic 0, the start

function of the ST pin is disabled and writing any non-zero value to the Sample Rate register will start a

mission. When the SE bit is set to a logic 1, the pushbutton method of starting a mission is enabled.

Under this mode of operation, the DS1615 will begin a datalog mission when a non-zero value has been

written to the Sample Rate register and then the ST pin has been held low for at least 0.5 seconds.

The sample rate during a datalog mission is equal to the value written to the Sample Rate register

multiplied by one minute. Writing a 0 to the MIP bit in the Status register completes the mission.

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Upon initiation of datalog mission by either method, the DS1615 will do two things:

1. The INSPEC and OUTSPEC pins will generate four low pulses simultaneously.

2. The Mission-in-Progress (MIP) bit in the Status register is set to a one.

The time at which the first datalog sample is measured is dependent upon the value in the Start Delay

registers. The two Start Delay registers provide a method for the end user to program a delay before

sampling commences. The delay is roughly equal to the value in the Start Delay registers times one

minute. For example, if the Start Delay registers contain a value of ten, then the device will begin

recording data approximately ten minutes after it received either the pushbutton start signal or start

instruction. The Start Delay registers are located at addresses 0012h and 0013h, with register 0012h

being the LSB and register 0013h being the MSB. The Start Delay register decrements every time the

Seconds register rolls over from 59 to 00. When this Start Delay register contains a 00, the first datalog

sample will be taken when the seconds register rolls over from 59 to 00.

The user has two options for dealing with the potential occurrence of a data overrun (i.e., more than 2048

total data samples). The first option is to enable the rollover feature of the DS1615. This is accomplished

by setting the Rollover bit (bit 3 of the Control register) to 1. When the Rollover feature is enabled, new

data is written over previous data, starting with address 0000h. For example, if the Datalog memory has

been completely filled (i.e., 2048 data samples have been recorded) the next data sample will be written

to address location 1000h and the address pointer will be incremented with each successive data sample.

The second option for dealing with data overrun is to stop the recording of data after the datalog memory

has been completely used. In other words, the DS1615 will stop recording data values after 2048 data

samples. This feature is enabled by disabling the Rollover feature. (bit 3 of the Control register set to 0).

It should be noted that during a datalog mission, a time stamp for the first sample is recorded, but is not

included for each subsequent sample. However, the time of acquisition for any data sample is easily

determined by considering the start time, the sample rate, the value in the Current Sample Counter, and

the address of the particular data sample in the datalog memory. If no rollover has occurred in the datalog

memory, the sample time associated with any particular data point can be calculated by multiplying the

address of the data by the sample rate and adding that to the stored start time value. If the rollover feature

has been enabled, the user can determine if rollover has occurred by reading the value in the Current

Samples register. This register counts the total number of samples that have been acquired. If this value

is greater than 07FFh (decimal 2047) then the user knows that rollover has occurred. If rollover has

occurred, the user needs to determine how many times rollover occurred in determining the sample time

for any particular data sample.

As a safety measure, the DS1615 has been designed such that the end user cannot write to the

Temperature Datalog Memory. This prevents the falsification of data-log data by writing values to

datalog registers.

DATA HISTOGRAM

While on a datalog mission, the DS1615 also records a histogram of the recorded temperature data. The

histo-gram is provided by a series of 63 two-byte data bins that are located in the Temperature Histogram

memory pages (addresses 0800h to 087Fh). Each bin consists of a 16-bit binary counter that is

incremented each time an acquired temperature value falls into the range of the bin. The least significant

byte of each bin is stored at the lower address. Bin 0 begins at memory address 0800h, bin 1 at 0802h,

and so on up to 087Ch for bin 62.

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After a temperature conversion is completed, the number of the bin to be updated is determined by

dropping the two least significant bits of the binary temperature value. Thus, bin 0 will be updated with

every temperature reading from -40°C to -38.5°C. In the same way, bin 1 is associated with the range of -

38°C to -36.5°C. Bin 62, finally, counts temperature values in the range of +84°C to 85.0°C. Since the

device will not generate temperature values higher than 85.0°C, bin 62 covers only three temperature

values. The memory for a potential 64 th bin exists, but will always read 0s.

Since each data bin contains two bytes, a total of 65,535 samples can be accumulated. If more samples

are measured, the data bin will remain at the maximum value. In other words, the data bin value will not

roll-over in the event of an overrun.

TEMPERATURE ALARM LOGGING

For some applications it may be essential to record exactly when a temperature sample exceeds a

predefined tolerance band and for how long the temperature violation remained.

A tolerance band is specified by means of the Temperature Alarm registers, addresses 000Bh and 000Ch.

The user can set a high and a low temperature threshold. As long as the temperature samples stay within

this tolerance band (i.e., are higher than the low threshold and lower than the high threshold), the DS1615

will not record any temperature alarm. If the temperature violates the temperature band, the DS1615 will

generate an alarm and set either the Temperature High Flag (THF) or the Temperature Low Flag (TLF) in

the Status register (address 0014h). In addition, the device generates a time stamp of when the alarm

occurred and records the duration of the alarming condition. The INT pin will be asserted by a high

temperature alarm if the Temperature High Interrupt Enable (THIE) is set and will be asserted by a low

temperature alarm if the Temperature Low Interrupt Enable (TLIE) is set.

The device stores a time stamp of a violating condition by copying contents of the three-byte Current

Samples Counter when the alarm occurred. The least significant byte is stored at the lower address. One

address higher than each time stamp, the DS1615 maintains a one byte duration counter that stores the

number of times the temperature was found to be beyond the threshold. If this counter has reached its

limit after 255 consecutive temperature readings and the temperature has not yet returned to a level within

the tolerance band, the device will issue another time stamp at the next higher address and open another

counter to record the duration. If the temperature returns to normal before the counter has reached its

limit, the duration counter of the particular time stamp will not increment any further. Should the

temperature again cross this threshold, another time stamp will be recorded and its associated counter will

increment with each temperature reading outside the tolerance band. This algorithm is implemented for

the low as well as for the high temperature threshold.

Time stamps and durations where the temperature violates the low temperature threshold are stored in the

address range 0220h to 024Fh (48 bytes). The memory address range 0250h to 027Fh (48 bytes) is

reserved for time stamps and duration where the temperature exceeds the high temperature threshold.

This allocation allows to record 24 individual alarm events and periods (12 periods for too hot and 12 for

too cold). The date and time of each of these periods can be determined from the Start Time Stamp and

the time distance between each temperature reading. Figure 2c illustrates the Alarm Time Stamps and

Durations register.

INSPEC AND OUTSPEC PINS

Two special output pins, INSPEC and OUTSPEC , are intended to output the status of the DS1615. More

specifically, these pins can be used to control the illumination of LEDs. For example, the INSPEC pin can

be used to pulse a green LED and the OUTSPEC pin can be used to pulse a red LED. When the end user

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starts a datalog mission or polls the device for information, one or both of these pins will be pulsed four

times. Depending on the status of the device, both pins will be pulsed simultaneously or just one pin will

be pulsed at a time. Each pulse is 62.5 ms in duration and will start every half second. See Figures 8 and

9 for further details.

The INSPEC and OUTSPEC pins are used to provide visual feedback to the end user in the following

situations:

1. Datalog Mission Start When a datalog mission is first initiated, the INSPEC and OUTSPEC pins will

generate four low pulses simultaneously to give the end user a visual indication that a datalog mission

has begun.

2. Request for Status of Data

Following a user request for the status of recorded temperature data, the INSPEC pin will generate four

low pulses if the recorded temperature data is within the user defined limits (as set in the Low

Temperature Threshold and High Temperature Threshold registers). If the recorded temperature data

contains any readings that fall outside of these thresholds, the OUTSPEC pin will be pulsed four times. If

the request comes after the mission has started (i.e., MIP = 1), but before the first temperature sample has

been recorded, the INSPEC and OUTSPEC pins will generate a total of four low pulses alternately, starting

with the OUTSPEC pin.

The DS1615 provides two methods for the user to request the status of the data. The first method is to

send the Specification Test command over the serial interface. The second method is by holding the ST

pin low for at least half a second after the datalogger has already been started.

CLOCK, CALENDAR, AND ALARM

The time and calendar information is accessed by reading/ writing the appropriate register bytes. Note

that some bits are set to zero. These bits will always read zero regardless of how they are written. The

contents of the time, calendar, and alarm registers are in the Binary-Coded Decimal (BCD) format.

The DS1615 can run in either 12-hour or 24-hour mode. Bit 6 of the hours register is defined as the 12-

or 24-hour mode select bit. When high, the 12-hour mode is selected. In the 12-hour mode, bit 5 is the

AM/PM bit with logic one being PM. In the 24-hour mode, bit 5 is the second 10-hour bit (20-23 hours).

The DS1615 also contains a time of day alarm. The alarm registers are located in registers 0007h to

000Ah. Bit 7 of each of the alarm registers are mask bits (see Table 2). When all of the mask bits are

logic 0, an alarm will occur once per week when the values stored in time-keeping registers 0000h to

0003h match the values stored in the time of day alarm registers. An alarm will be generated every day

when mask bit of the day alarm register is set to 1. An alarm will be generated every hour when the day

and hour alarm mask bits are set to 1. Similarly, an alarm will be generated every minute when the day,

hour, and minute alarm mask bits are set to 1. When day, hour, minute, and seconds alarm mask bits are

set to 1, an alarm will occur every second.

As a security measure to prevent unauthorized tampering, changing any value in the RTC and Control

registers (with the exception of the Status register) will stop a datalog mission and clear the Mission-in-

Progress (MIP) bit.

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TIME OF DAY ALARM BITS Table 2

ALARM REGISTER MASK BITS (BIT 7)

SECONDS MINUTES HOURS DAYS

1 1 1 1 Alarm once per second

0 1 1 1 Alarm when seconds match

0 0 1 1 Alarm when minutes and seconds match

0 0 0 1 Alarm when hours, minutes, and seconds match

0 0 0 0 Alarm when day, hours, minutes, and seconds match

SPECIAL PURPOSE REGISTERS

The following description defines the operation of the special function registers of the DS1615.

CONTROL REGISTER

MSb LSb

EOSC CLR 0 SE RO TLIE THIE AIE

EOSC - Enable oscillator - This bit controls the state of the oscillator in battery back-up mode only.

When set to logic 0, the oscillator is active. When this bit is set to a logic 1, the oscillator is stopped and

the DS1615 is placed into a low-power standby mode with a current drain of less than 100 nanoamps at

room temperature. When VCC is applied or when MIP =1, the oscillator is active regardless of the state of

this bit.

CLR - Clear Enable This bit enables the Clear Memory command. When this bit is set to a one and the

Clear Memory command is subsequently issued, the datalog, histogram, Temperature Alarm, Current

Samples, Start Time Stamp, Start Delay, and Sample Rate register are all cleared to zero. Following the

issuing of the Clear Memory command, the CLR bit is also cleared to zero. If the Clear Enable bit is set,

but a command other than the Clear Memory command is issued next, the CLR bit is cleared to a zero

and the contents of the datalog, histogram, temperature alarms, Current Samples registers, Start Delay,

and Sample Rate register are unchanged.

ST - Start Enable - This bit enables the start function of the ST input. When SE is a logic 1, the ST input

is enabled as the start pin for datalogging operation. When enabled, datalogging operation begins when

the Sample Rate register contains a non-zero value AND then the ST pin has been held low for at least

0.5 seconds. When SE is a logic 0, writing any non-zero value to the Sample Rate register will start

datalogging operation.

Once datalog operation has been initiated, the first data sample occurs after the specified delay written to

the Start Delay register has elapsed.

RO - Roll-Over - This bit determines whether the data-log function of the DS1615 rolls over or stops

writing data to the datalog memory in the event that the datalog memory is completely filled. If RO is set

to a 1, the data-log memory will roll over after all 2048 registers in the datalog memory have been used.

In other words, after the 2048th data sample, the following sample will be written to register 0000h,

overwriting the original data. Likewise, subsequent samples will increment through the datalog registers,

overwriting their data. If RO is cleared to a 0, no further data samples will be written to the datalog

memory after all datalog memory registers have been filled. Samples, however, will continue to be taken

and the appropriate histogram registers will be incremented with each sample. Likewise, the temperature

alarms will also continue to function.

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TLIE - Temperature Low Interrupt Enable - When set to a logic 1, this bit permits the Temperature Low

Flag (TLF) in the Status register to assert INT . When the TLIE bit is set to logic 0, the TLF bit does not

initiate the INT signal.

THIE - Temperature High Interrupt Enable - When set to a logic 1, this bit permits the Temperature High

Flag (THF) in the Status register to assert INT . When the THIE bit is set to logic 0, the THF bit does not

initiate the INT signal.

AIE - Alarm Interrupt Enable - When set to a logic 1, this bit permits the Alarm Flag (ALMF) in the

Status register to assert INT . When the AIE bit is set to logic 0, the ALMF bit does not initiate the INT

signal.

STATUS REGISTER

MSb LSb

TR MEMCL MIP SIP LOBAT TLF THF ALMF

TR - Temperature Ready This bit indicates the status of the temperature value in the Current Temperature

has completed the temperature measurement and has written a valid value to the Current Temperature

cleared to 0 when the Read Temperature command is sent.

MEM CLR - Memory Cleared This bit indicates that the datalog memory, histogram memory,

Temperature Alarm, Current Samples, Start Time Stamp, Start Delay, and Sample Rate registers are all

cleared to zero. MEM CLR is cleared to 0 when a datalog mission is started (i.e., MIP = 1).

MIP - Mission in Progress This bit indicates the sampling status of the DS1615. If MIP is a logic 1, the

device is currently on a mission in which it is operating in the datalogging mode. The MIP bit is changed

to a logic 1 immediately following 1) the writing of a non-zero value to the Sample Rate register when

the SE bit is a 0 or 2) a 0.5 second pulse on the ST pin if the Sample Rate register contains a non-zero

value AND the SE bit is a 1.

If MIP is a logic 0, the DS1615 is not currently in datalogging mode. The MIP bit transitions from a

logic 1 to a logic 0 whenever datalogging is stopped. Datalogging is stopped when the DS1615 is cleared

via the clear bit and clear instruction or when any of the RTC or Control registers (with the exception of

the Status register) are written to during a mission. The MIP bit can also be written to a logic 0 by the

end user to stop datalogging. It cannot, however, be written to a logic 1.

SIP - Sample in Progress This bit indicates that the DS1615 is currently in the process of acquiring a

temperature sample. When the SIP bit is 0, a temperature conversion is not currently in process and the

next conversion will not begin for at least 250 ms. When the SIP bit is a 1, a temperature conversion is in

progress and no registers or memory locations should be read or written. The SIP bit will be a 1 for a

maximum of 750 ms.

LOBAT - Low Battery Flag - This bit reflects the status of the backup power source connected to the

VBAT pin. A logic one for this bit indicates an exhausted lithium energy source.

DS1615

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TLF - Temperature Low Flag - A logic 1 in the Temperature Low Flag bit indicates that the temperature

is/has been less than or equal to the value in the Temperature Low Threshold register. If TLIE is also a

logic 1, the INT pin will go low. TLF is cleared by writing this bit to a logic 0.

THF - Temperature High Flag - A logic 1 in the Temperature High Flag bit indicates that the temperature

is/has been greater than or equal to the value in the Temperature High Threshold register. If THIE is also

a logic 1, the INT pin will go low. THF is cleared by writing this bit to a logic 0.

ALMF - Alarm Flag - A logic 1 in the Alarm Flag bit indicates that the current time has matched the time

of day Alarm registers. If the AIE bit is also a logic 1, the INT pin will go low. ALMF is cleared by

writing this bit to a logic 0.

SAMPLE RATE REGISTER

MSb LSb

SR7 SR6 SR5 SR4 SR3 SR2 SR1 SR0

The data sample rate for the DS1615 can range from once per minute to once per 255 minutes. The rate

is equal to the value written to the Sample Rate register multiplied by one minute.

This register can only be written to a new value when the MEM CLR bit in the Status register is set to 1.

In other words, once a datalog mission has started, it cannot be changed without first issuing the Clear

Memory command.

The Sample Rate register is cleared by issuing the Clear Memory command.

START DELAY RESISTER

MSb LSb

D15 D14 D13 D12 D11 D10 D9 D8

D7 D6 D5 D4 D3 D2 D1 D0

The Start Delay register determines the amount of delay before the DS1615 begins to take temperature

measurements. The amount of the delay is roughly equal to the value in the register multiplied by one

minute. If the register contains 00h, the first sample will begin when the seconds register rolls over from

59 to 00.

The value in this register decrements each time the seconds register rolls over from 59 to 00 until the Start

Delay register reaches a value of 00h.

TEMPERATURE HIGH THRESHOLD REGISTER

MSb LSb

TH7 TH6 TH5 TH4 TH3 TH2 TH1 TH0

This register determines the high threshold for interrupt generation from the thermal sensor. If the

temperature is greater than or equal to the value in this register, an interrupt will be activated if the

Temperature High Interrupt Enable (THIE) bit is set to a logic 1.

TEMPERATURE LOW THRESHOLD REGISTER

MSb LSb

TL7 TL6 TL5 TL4 TL3 TL2 TL1 TL0

DS1615

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This register determines the low threshold for interrupt generation from the thermal sensor. If the

temperature is less than or equal to the value in this register, an inter-rupt will be activated if the

Temperature Low Interrupt Enable (TLIE) bit is set to a logic 1.

CURRENT TEMPERATURE REGISTER

MSb LSb

CT7 CT6 CT5 CT4 CT3 CT2 CT1 CT0

This register provides the most recently acquired temperature measurement. It contains either the most

recently measured sample from automatic datalogging or it contains data that was acquired in response to

a users instruction for an immediate temperature measurement. An immediate measurement is acquired

by issuing the Read Temperature command.

After issuing the Read Temperature command, the value in this register is valid only if the Temperature

Ready (TR) bit in the Status register is a logic 1.

CURRENT SAMPLES COUNTER

This three-byte register set provides the number of samples that have been logged during the current data

logging operation (also known as a “mission”). The con-tents of this register can be used by software to

point to the most recent data sample in the Datalog NV RAM. The data in these registers are cleared by

enabling and issuing the Clear Memory command.

TOTAL SAMPLES COUNTER

This three-byte register set provides the total number of data samples that have been logged during the

life of the product. This value cannot be written by the end user. The value in this register is maintained

as long as the lithium energy source is available.

SILICON SERIAL NUMBER

A unique 64-bit lasered serial number is located in the register bank. This serial number is divided into

three parts. The first byte contains a model number (17h) to identify the device type. The next six

registers contain a unique binary number. The last serial number byte contains a CRC byte used to

validate the data in the first seven serial number registers. All eight bytes of the serial number are read

only registers.

The DS1615 is manufactured such that no two devices will contain an identical serial number. Blocks of

numbers can be reserved by the customer. Contact Dallas Semiconductor for special ordering

information for devices with reserved blocks of serial numbers.

SECURITY

The DS1615 provides several measures to insure data integrity for the end user. These security measures

are intended to prevent third party intermediaries from tampering with the data that has been stored in the

Datalog and Histogram memory.

As a first security measure, the Datalog and Histogram memory are Read-only from the perspective of the

end user. The DS1615 can write sampled data into these memory banks, but the end user cannot write

data to individual registers. This prevents an unscrupulous intermediary from writing false data to the

DS1615. The end user, however, can clear the contents of the Datalog and Histogram memory. This is

accomplished by enabling and issuing the Clear Memory command.

DS1615

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A second security feature lies in the fact that once the sample rate has been selected by writing to the

Sample Rate register, it cannot be changed to another value without resetting the recorded temperature

data. This prevents gathering many data samples at a fast sample rate and then lowering the sample rate

to give the appearance that the data was recorded over a longer period of time. The Sample Rate register

can only be written to a new value if the MEM CLR bit is set to one.

A third security feature lies in the two integrated sample counters - the Current Samples Counter and the

Total Samples Counter. These two counters can be used to guarantee that the DS1615 data has not been

cleared at any time during a given period of time. The Current Samples Counter counts the number of

samples that have occurred since the most recent data acquisition operation was started (i.e., the number

of samples since the Sample Rate register was written to a non-zero value). The Total Samples Counter

counts the total number of samples that have been recorded in the life of the device (assuming the lithium

energy source has not been removed during that time). If the end user knows the value in the Total

Samples Counter before the data acquisition operation is started, he can guarantee that the DS1615 has

not been cleared. If the Current Samples count equals the difference between the ending value and

beginning value of the Total Samples Counter, then the DS1615 data has not been cleared during that

time frame.

As a fourth security measure, changing any value in the RTC and Control registers (with the exception of

the Status register) will stop datalogging and clear the Mission-in-Progress (MIP) bit.

SERIAL INTERFACE

The DS1615 provides two different serial communications options; asynchronous and synchronous. Both

communications options will transmit the data LSb first, MSb last.

The mode of communication is selected via the COMSEL pin. When this pin is pulled high, the DS1615

operates in synchronous mode. In this mode, communication with the DS1615 is facilitated by the

SCLK, I/O, and RST pins. When COMSEL is pulled low or floated, asynchronous communications is

selected and communication with the device occurs over the TX and RX pins. The operation of each

mode is discussed in further detail below.

Asynchronous Communication

In asynchronous mode, the DS1615 operates as a slave peripheral device which is read and written over a

half duplex asynchronous data interface at the fixed rate of 9,600 bits per second. Data is received and

transmitted in 8-bit bytes using a standard asynchronous serial communications format as shown in

Figure 3. This format is easily generated by the UART in most systems. The DS1615 data format

implements 10 bit words including one start bit, eight data bits, and one stop bit. Data is received by the

DS1615 on the RX pin and transmitted by the TX pin.

COMMUNICATION WORD FORMAT Figure 3

DS1615

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Synchronous Communication

Synchronous communication is accomplished over the 3-wire bus which is composed of three signals.

These are the RST (reset), the SCLK (serial clock), and I/O (data I/O) pins. The 3-wire bus operates at a

maximum data rate of 2 Mbps. All data transfers are initiated by driving the RST input high and are

terminated by driving RST low. (See Figures 6 and 7.) A clock cycle is a sequence of a falling edge

followed by a rising edge. For data inputs, the data must be valid during the rising edge. Data bits are

output on the falling edge of the clock and remain valid through the rising edge.

When reading data from the DS1615, the I/O pin goes to a high impedance state when the clock is high.

Taking RST low will terminate any communication and cause the I/O pin to go to a high impedance state.

General Communications Format

Communication with the DS1615 in both synchronous and asynchronous modes is accomplished by first

writing a command to the device. The command is then followed by the parameters and/or data required

by the command. The command set for the DS1615 can be seen in Table 3. Reads and writes to the

DS1615 differ in that writes are performed one byte at a time while reads are performed in page long (up

to 32 byte) bursts. Writing one byte at a time means that a write command has to be issued before each

byte of data that is written. For example, writing to the user NV RAM requires that the Write User NV

RAM command be writ-ten followed by the address to be written and then the actual data byte. Writing a

second data byte would require the same procedure with a new address specified. Reads, however, are

accomplished in bursts. For example, if an end user wants to read data from a specific page he would

first issue the Read Page command, followed by the address to begin reading. After the DS1615 receives

the command and starting address, it will immediately transmit the data that resides at the given address

location. However, rather than stop with that single byte of data, the DS1615 will continue transmitting

the next byte of data and will continue transmitting data until the page boundary is reached. A page read

can begin at any address, but will always end at the page boundary. Thus, a page read can range from 1

to 32 bytes. It should be noted that a read can be terminated at any time when communicating in

synchronous mode by pulling RST to ground. However, in asynchronous mode, the DS1615 will not

stop transmitting data until the page boundary is reached.

Cyclical Redundancy Check (CRC)

When communicating in the asynchronous mode, a 16-bit CRC is transmitted by the DS1615 following

the transmission of all data. When communicating in synchronous mode, no CRC is transmitted.

The 16-bit CRC (Cyclical Redundancy Check) is used to insure the accuracy of the data that is read from

the DS1615. The CRC is generated according to the standardized CRC16-polynomial function X16+ X15+

X2 1. Figure 4 illustrates the function of the generator. The CRC is generated by clearing the CRC

generator and then shifting in data from the register set being read. A sixteen bit CRC is transmitted by

the DS1615 after the last register of any page of memory is read. In other words, a CRC is generated at

the end boundary of every page that is read.

DS1615

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CRC HARDWARE DESCRIPTION AND POLYNOMIAL Figure 4

Communication Reset (Asynchronous Mode)

When transmitting the command, parameters, or data to the DS1615, it is possible that communication

might be interrupted. For example, the user might accidentally disconnect the cable linking the device to

the host computer. To insure that communication always starts at a known state when in the

asynchronous mode, the DS1615 will reset the communication if it senses a problem. This is

accomplished via two methods. First, if during the transmission of a byte of data to the DS1615, the stop

bit is not received, communication will be reset. The lack of a valid stop bit indicates that that particular

byte of data was not received correctly. Second, if more then 10-bit times expire between the reception of

one byte of data and the reception of the next required byte, then communication will be reset.

Automatic resetting of communication is not required when communicating in the synchronous mode.

This is because of the function of the RST pin. Pulling RST low resets the serial communication of the

DS1615.

DS1615 COMMANDS

All communication with the DS1615 is accomplished by writing a command to the device followed by

parameter byte/s if required. Table 3 illustrates the commands sup-ported by the DS1615.

DS1615 COMMANDS Table 3

COMMAND FUNCTION DESCRIPTION

22h Write Byte Write one byte to RTC, Control registers, and User NV RAM

33h Read Page Read Page

44h Specification

Test

Poll status of temperature extremes

55h Read

Temperature

Instructs DS1615 to immediately measure the temperature and store the

result in the Current Temperature register when MIP = 0.

A5h Clear

Memory

This command clears the datalog, histogram, Temperature Alarm,

Current Samples, Start Time Stamp, Start Delay, and Sample Rate

registers when the Clear Enable bit (CLR) in the Control register is set

to a one.

The DS1615 commands are summarized below. Note that if an invalid command is issued, no action is

taken by the device.

DS1615

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1. Write Byte (22h)

Host Transmit:

D7 D6 D5 D4 D3 D2 D1 D0

00100010

0 a6a5a4a3a2a1a0

d7 d6 d5 d4 d3 d2 d1 d0

DS1615 Response: None

Note that good programming practice insists that the Clear Memory command should be issued whenever

the DS1615 is programmed to begin a new datalogging mission.

2. Read Page (33h)

Host Transmit:

D7 D6 D5 D4 D3 D2 D1 D0

00110011

a15 a14 a13 a12 a11 a10 a9 a8

a7 a6 a5 a4 a3 a2 a1 a0

DS1615 Response (Host Receives):

D7 D6 D5 D4 D3 D2 D1 D0

↓

Where xxx represents the last register of the page that has been accessed.

When in asynchronous mode, the TX pin becomes inactive after the last register in the page and the CRC

have been transmitted. In synchronous mode, the DS1615 will continue to transmit data as long as clocks

are presented to the serial interface. If clocks are presented after the final data bit of the last register in

the page, the DS1615 will wrap-around to the first register in the page and sequentially transmit data as

long as the clocks continue.

3. Specification Test (44h)

Host Transmit:

D7 D6 D5 D4 D3 D2 D1 D0

01000100

DS1615 Response (Host Receives): Either the INSPEC or OUTSPEC pin will generate four low pulses.

Each pulse will be 62.5 ms in duration and will start every half second.

This command instructs the DS1615 to generate four low pulses on either the INSPEC or OUTSPEC LED

driver pins. The pin that is driven is dependent upon whether any data samples fell outside of the High

Temperature and Low Temperature Threshold boundaries. These pins, when used to drive LEDs, can be

used to provide a quick visual confirmation as to whether the temperature remained within the user-

defined limits.

DS1615

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Note that the Specification test command is ignored if the ST button is pulled to ground when the

command is issued.

4. Read Temperature (55h)

Host Transmit:

D7 D6 D5 D4 D3 D2 D1 D0

01010101

DS1615 Response (Host Receives): When the device is not currently datalogging (i.e., MIP = 0), the

Temperature is immediately measured and value is written to the Current Temperature register.

This command instructs the DS1615 to immediately perform a temperature measurement and to store the

resulting value in the Current Temperature register. The temperature value obtained from this command

is not stored in the datalog or histogram memory. After this command has been executed, the user must

read the Temperature Ready (TR) bit in the Status register to determine if the temperature measurement

has been completed. If the TR bit is a logic 1, the measurement has been completed and the value in the

Current Temperature register is valid. If the TR bit is a logic 0, the measurement has not been completed.

This command functions only when MIP = 0 (i.e., the device is not currently datalogging). If MIP =1, the

DS1615 takes no action in response to the command.

5. Clear Memory (A5h)

Host Transmit:

D7 D6 D5 D4 D3 D2 D1 D0

10100101

DS1615 Response: The contents of the datalog, histogram, Temperature Alarm, Current Samples, Start

Time Stamp, Start Delay, and Sample Rate registers are cleared if the Clear Memory command has been

enabled by setting the CLR bit in the Control register to a one. After clearing the memory, the MEM

CLR bit in the Status register is set. The Clear Memory command functions only if the oscillator is

active. The DS1615 is inaccessible for 500 µs after the Clear Memory command has been issued.

DS1615

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ABSOLUTE MAXIMUM RATINGS*

Voltage on Any Pin Relative to Ground -0.3V to +7.0V

Operating Temperature -40°C to +85°C

Storage Temperature -55°C to +125°C

Soldering Temperature See J-STD-020A specification

✻This is a stress rating only and functional operation of the device at these or any other conditions above

those indicated in the operation sections of this specification is not implied. Exposure to absolute

maximum rating conditions for extended periods of time may affect reliability.

RECOMMENDED DC OPERATING CONDITIONS (-40°C to 85°C)

PARAMETER SYMBOL MIN TYP MAX UNITS NOTES

Power Supply Voltage VCC 4.0 5.0 5.5 V 1

Input Logic 1 VIH 2.2 VCC +0.3 V 1

Input Logic 0 VIL -0.3 +0.8 V 1

Battery Voltage VBAT 2.7 90%VCC V1

DC ELECTRICAL CHARACTERISTICS (-40°C to 85°C)

PARAMETER SYMBOL MIN TYP MAX UNITS NOTES

Input Leakage ILI -1 +1 µA

Input Leakage COMSEL pin ILIC 100 200 µA

Logic 1 Output VOH 2.4 V

Logic 0 Output VOL 0.4 V

TX and I/O Pins Output

Current @ 2.0V

IOH -2.2 mA

TX, I/O, and INT Pins Output

Current @ 0.8V

IOL 4mA

INSPEC and OUTSPEC Output

Current @ 0.8V

IOL 10 mA

Active Supply Current ICCA 210mA

Temperature Conversion

Current

ITC 600 µA

Oscillator Current IOSC 300 500 nA

Battery Standby Current

(Oscillator Off)

IBAT 200 nA

DS1615 Thermometer Error TERR ±2.0 °C6

CAPACITANCE (TA = 25°C)

PARAMETER SYMBOL MIN TYP MAX UNITS NOTES

Input Capacitance CI10 pF

Crystal Capacitance CX6pF

DS1615

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AC ELECTRICAL CHARACTERISTICS (-40°C to +85°C; VCC=5.0V ±10%)

PARAMETER SYMBOL MIN TYP MAX UNITS NOTES

Vcc rise/fall time tR/tF3 500 ms

Delay from ST to INSPEC or

OUTSPEC Active

tSS 560 ms

Delay from Specification to

INSPEC or OUTSPEC Active

tCS 560 ms

Temperature Conversion Time tCONV 150 200 ms

INSPEC and OUTSPEC Active

Low Pulse Width

tSL 62.5 ms

INSPEC and OUTSPEC High

Duration

tSH 437.5 ms

ASYNCHRONOUS INTERFACE TIMING (-40°C to +85°C; VCC=5.0V ±10%)

PARAMETER SYMBOL MIN TYP MAX UNITS NOTES

Date Rate f BIT 9,408 9,600 9,792 bits/sec 2

Turnaround Time tTURN 2/fBIT s

SYNCHRONOUS (3-WIRE) SERIAL

INTERFACE TIMING (-40°C to 85°C; VCC=5.0V ±10%)

PARAMETER SYMBOL MIN TYP MAX UNITS NOTES

Data to SCLK Setup tDC 50 ns 3

SCLK to Data Hold tCDH 70 ns 3

SCLK to Data Delay tCDD 200 ns 3,4, 5

SCLK Low Time tCL 250 ns 3

SCLK High Time tCH 250 ns 3

SCLK Frequency tCLK DC MHz 3

SCLK Rise and Fall tR , tF2.0 ns

RST to SCLK Setup tCC 1 500 µs3

SCLK to RST Hold tCCH 60 ns 3

RST Inactive Time tCWH 1µs3

RST to I/O High Z tCDZ 70 ns 3, 7

SCLK to I/O High Z tCCZ 70 ns 3, 7

NOTES:

1. All voltages are referenced to ground,

2. The data rate fBIT is equal to 1/tBIT

3. Measured with VIH= 3.0V or VIL= 0.0V and 10 ns maximum rise and fall time.

4. Measured at VOH=2.4V or VOL=0.4V.

5. Load Capacitance = 50 pF.

6. Thermometer error reflects temperature error as tested during calibration.

7. Sampled with 5 pF load. Not 100% tested.

DS1615

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POWER-UP/DOWN WAVEFORM TIMING Figure 5

ASYNCHRONOUS SERIAL INTERFACE TIMING Figure 5

SYNCHRONOUS (3-WIRE) SERIAL INTERFACE READ TIMING Figure 6

SYNCHRONOUS (3-WIRE) SERIAL INTERFACE WRITE TIMING Figure 7

tFtR

Vcc

0.25V

4.75V

DS1615

24 of 24

SPECIFICATION POLLING FROM ST INPUT Figure 8

SPECIFICATION POLLING FROM COMMAND Figure 9

INSPEC

OUTSPEC

tSS

tSl tSh

INSPEC

OUTSPEC

start data = 55h stop

tCS

tSl tSh