MEMSIC MXC6232xE/F Rev.A Page 8 of 9 4/11/2010
Even though each axis consists of two bytes, which are 16-
bits of data, the actual accelerometer resolution is limited
to either 12 bits or 10 bits, which depends on an internal
output register refresh rate. Unused MSB’s will be simply
filled by “0”s.
Note that temperature output shares the same registers with
X channel output. Customer can select which signal needs
to be read out by using TOEN bit.
Resolution 10 bits 12 bits
Refreshing rate 400Hz 100Hz
Zero-G Offset 512 2048
Note: 20mS (MXC6232xE) and 5mS (MXC6232xF)
typical waiting time is necessary between each data
acquisition.
The master can stop slave data transfer after any of the five
bytes by not sending an acknowledge command and
followed by a “STOP” condition.
POWER DOWN MODE
The Memsic accelerometer can enter a power down mode
by the master device writing a code of [xxxxxxx1] into the
accelerometer’s internal register. A wake up operation is
performed when the master writes into the same register a
code of [xxxxxxx0]. Note that the MXC6232xE/F needs
about 75mS (typical) for power up time.
EXAMPLE OF DATA COMMUNICATION
First cycle: START followed by a calling to slave address
[0010xxx] to WRITE (8th SCL, SDA keep low). [xxx] Is
determined by factory programming, a total of 8 different
addresses are available.
Second cycle: After an acknowledge signal is received by
the master device (Memsic device pulls SDA line low
during 9th SCL pulse), master device sends “[00000000]”
as the target address to be written into. Memsic device
should acknowledge at the end (9th SCL pulse). Note: since
Memsic device has only one internal register that can be
written into, user should always indicate “[00000000]” as
the write address.
Third cycle: Master device writes to internal Memsic
device memory code “[xxxxxxx0]” as a wake-up call. The
Memsic device should send acknowledge signal. A STOP
command indicates the end of write operation. A 75msS
(typical) wait period should be given to Memsic device to
return from a power-down mode. The delay value depends
on the type of Memsic device. Generally speaking, low
power products tend to have longer startup time.
Fourth cycle: Master device sends a START command
followed by calling Memsic device address with a WRITE
(8th SCL, SDA keep low). An “acknowledge” should be
sent by Memsic device at the end.
Fifth cycle: Master device writes to Memsic device a
“[00000000]” as the starting address for which internal
memory is to be read. Since “[00000000]” is the address
of internal control register, reading from this address can
serve as a verification of operation and to confirm the write
command has been successful. Note: the starting address in
principle can be any of the 5 addresses. For example, user
can start read from address [0000001], which is X channel
MSB.
Sixth cycle: Master device calls Memsic device address
with a READ (8th SCL cycle SDA line high). Memsic
device should acknowledge at the end.
Seventh cycle: Master device cycles SCL line, first
addressed memory data appears on SDA line. If in step 7,
“[00000000]” was sent, internal control register data
should appear (in the following steps, this case is
assumed). Master device should send acknowledge at the
end.
Eighth cycle: Master device continues cycle SCL line, next
byte of internal memory should appear on SDA line (MSB
of X channel). The internal memory address pointer
automatically moves to the next byte. Master
acknowledges.
Ninth cycle: LSB of X channel. In the case that TOEN bit
of internal register was set to “1”, the MSB and LSB of
TOUT (temperature) should appear in last two steps.
Tenth cycle: MSB of Y channel.
Eleventh cycle: LSB of Y channel.
Master ends communications by sending NO acknowledge
and followed by a STOP command. Note: if mater device
continues to cycle SCL line, the memory pointer will go to
sixth and seventh positions, which always have
“[00000000]”. After seventh position, pointer will go to
zero again.
Optional: Master powers down Memsic device by writing
into internal control register. (See step 1 through 4 for
WRITE operation)