Alesis Semiconductor
DS3201-0402 12555 Jefferson Blvd., Suite 285
Los Angeles, CA 90066
Phone (310) 301-0780 Fax (310) 306-1551 www.alesis-semi.com
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General Description
The AL3201B (SCR, or Single Chip Reverb)
is a one chip reverb solution that is
compact, easy to use, and yet quite
powerful. Built-in DRAM eliminates the
need for wide bus connections to external
RAM, and the choice of built-in programs
and a user programmable RAM allows
instant usability or custom program
design.
Features
G
16 internal ROM programs consisting
of halls, rooms, plates, delays, chorus,
flange, vocal cancel, and rotary
speaker emulation.
G
Serially programmable SRAM (Writable
Control Store – WCS) for program
development or dynamically changing
programs
G
Programs run at 128 instructions per
word clock. (6 MIPS @ 48kHz sam-
pling frequency.)
G
32k location DRAM provides over 0.68s
of delay at 48kHz sampling frequency.
G
Internal crystal oscillator circuit
eliminates need for discrete external
passive components.
G
Internal voltage regulators allow opera-
tion from 5.5V down to 3.0V VDD.
G
Internal 1000pF bypass capacitor to
reducevoltageswingsattherails.
Applications
G
Personal stereos with reverb functions.
G
Extremely portable guitar effects boxes.
G
Karaoke machines utilizing the vocal cancel program.
G
Hardware reverb effects for computer sound cards.
G
Ambience settings for car stereos.
DigOut
Int/Ext
XtalIn
XtalOut
Prog0/SData
Prog1/SClk
Prog2
Prog3
DigIn
Bypass
Gnd
Reset
SysClk
BitClk
WordClk
16 pin SOIC
300 mils wide
18
16
9
VDD
AL3201B
SCR
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Electrical Characteristics and Operating Conditions
Parameter Description Condition Min Typ Max Units
Electrical Characteristics and Operating Conditions
VDD 5Supply Voltage 3.0 5.0 5.5 V
IDD Supply Current : SCR 9 10 11 mA
Gnd 3Ground - 0.0 - V
FSSample rate 24 148 50 1kHz
Temp Temperature 0 25 70 °C
Outputs (DigOut, SysClk, BitClk, WordClk)
VOH Logical “1” output voltage Unloaded 0.9 VDD VDD -V
V
OL Logical “0” output voltage Unloaded - 0 0.05 VDD V
IOH Logical “1” output current VDD=5V VO=4.5V - - -8.0 mA
IOL Logical “0” output current VDD=5V VO=0.4V - - 8.0 mA
_______________ _____________ _____________
Inputs (DigIn, Int/Ext, Prog0/Sdata, Prog1/SClk, Prog2, Prog3, Reset)2,4
VIH Logical “1” input voltage 2.5 - VDD V
VIL Logical “0” input voltage 0 - 0.5 V
IIH Logical “1” input current VDD=VIH=5V --2
µA
I
IL Logical “0” input current No pullup pin --2
µA
I
ILP Logical “0” input current Pullup pin, Vin=0 83 167 333 µA
CIN Input Capacitance - 2.0 - pF
Notes:
1. Changing the sample rate (by changing the crystal frequency) will change the maximum delay
available through the DRAM proportionally. Low sample rates require more refresh instructions.
2. XtalIn, XtalOut are special pins designed to be connected to a crystal. XtalOut is a relatively weak pin
(about 0.2 mA) and should not be used to drive external circuits. Instead of using a crystal, XtalIn
maybedrivenbyastandardV
DD to Gnd logic signal, but the logic levels are not specified.
3. All other voltages are relative to Gnd.
4. Bypass (pin 14) must never exceed 3.6V
5. If VDD will always be below 3.6V (including the effects of ripple, spikes, etc.) then the Bypass pin
should be connected to VDD.
Pin Descriptions: AL3201B SCR (*: Pullup to VDD via nominal internal 30kΩresistor)
Pin # Name Pin Type Description
1 DigOut Output Digital serial output for stereo DAC.
2______________
Int/Ext Input* Internal/external program selection. 1:Internal, 0:External.
3 XtalIn Input 12.288MHz crystal input.1
4 XtalOut Output 12.288MHz crystal output.1
5 Prog0/SData Bidirectional* Internal program select 0 / serial interface data line.
6 Prog1/SClk Input* Internal program select 1 / serial interface clock line.
7 Prog2 Input* Internal program select 2.
8 Prog3 Input* Internal program select 3.
9 WordClk Output Word clock output.
10 BitClk Output Bit clock output.
11 SysClk Output System clock output.
12 _______________ ______
Reset Input Active low reset.
13 Gnd Ground Ground connection.
14 Bypass 2Bidirectional Connect 0.1µF bypass capacitor to Gnd for internal regulator.
15 VDD Power VDD power pin. Connect 0.1µFcapacitortoGnd.
16 DigIn Input Digital serial input from stereo ADC.
Note:
1. Internal 18pF capacitor to ground. Internal 120kΩresistor between Xtal pads.
2. If VDD will always be below 3.6V (including the effects of ripple, spikes, etc.) then the Bypass pin should be
connected to VDD.
Alesis Semiconductor
DS3201-0402 12555 Jefferson Blvd., Suite 285
Los Angeles, CA 90066
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Block Diagram
Mechanical Specification
18
916
E
D
F
H
GL
K
7° nom
B
C
4° nom
J
A
Dimensions (Typical)
Inches Millimeters
A.406” 10.31
B .295” 7.49
C .407” 10.34
D .100” 2.50
E .008” 0.20
F .025” 0.64
G .050” 1.27
H .017” 0.42
J .011” 0.27
K .340” 8.66
L .033” 0.83
Notes:
1) Dimension “A” does not include mold
flash, protrusions or gate burrs.
Alesis Semiconductor
DS3201-0402 12555 Jefferson Blvd., Suite 285
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Internal Programs
TheSCRcomeswith16internalROM
programs ready to go, utilizing the skills
and techniques of the Alesis Studio
Electronics effects processor programmers.
By setting the chip to internal mode, the
four program pins may be used to select
between the different algorithms.
Program List
Prog[3:0] Name Description
0110 Hall 1 Bright hall reverb for drums, guitars, and vocals.
0010 Hall 2 Warm hall for acoustic guitars, pianos, and vocals.
1010 Room 1 Hardwood studio for acoustic instruments.
1110 Room 2 Ambience for acoustic mixes and synth sounds.
1111 Room 3 Warm room for guitars and rhythm instruments.
1011 Plate 1 Classic plate reverb for lead vocals and instruments.
1001 Plate 2 Sizzling bright plate reverb for vocals and drums.
1101 Plate 3 Short vintage plate reverb for snares and guitars.
1100 Chorus Stereo chorus for guitars and pianos.
1000 Flange Stereo flanger for jet wash effects.
0000 Delay 1 125ms slapback delay for vocals and guitars.
0100 Delay 2 190ms delay for percussive arpeggios.
0101 Chorus/Room 1 Chorus with reverb for guitars, synths, and pianos.
0001 Chorus/Room 2 Auto-wah guitar effect with reverb for lead instruments.
0011 Vocal Cancel Removes lead vocals from many stereo recordings.
0111 Rotary Speaker Rotary speaker emulation for organs and guitars.
Note:
The unusual ordering of the programs allows a 16-position rotary switch’s Gray code output
to be connected to the program pins.
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Programming the RAM
Alongside the 16 internal programs is an
externally programmable SRAM that is
easily accessible through the serial clock
and data pins. By setting the chip to
external mode, the SClk and SData pins
become available for serial
communication. Except for its external
programmability, there is no functional
difference between the SRAM and the
internal ROMs.
Memory Map
Addr Name
Addr Name
0:3 LFO Coefficients0:127 WCS RAM 4:127 MAC Instructions
128 Control/Status 0
129 Control/Status 1
A simple assembly language is available
for writing programs. With the assembler
and loader software available from the
Alesis Semiconductor website, programs
may be developed on the PC and
downloaded into the chip. Please refer to
theassemblylanguageguideforafull
description.
LFO Coefficient Word
Bit # Description
31 P: Pitch shift mode select (S must be set). 1
30 S: Sine/triangle select. 1:Triangle; 0: Sine.
X[1:0] Xfade
11 1/16
10 1/8
01 1/2
29:28
X[1:0]: Crossfade
coefficient select. Value
indicates the fraction of a
half sawtooth period
used in crossfading. 00 1
27:15 F[12:0]: Frequency coefficient, unsigned.
14:0 A[14:0]: Amplitude coefficient, unsigned.
Note:
If set, the output waveform is a sawtooth with double
the triangle wave’s frequency.
Sawtooth SIN
Sawtooth COS
Crossfade 1
Crossfade 1/2
Crossfade 1/8
The first four instructions in the WCS RAM
set the parameters for the four LFOs. The
sinusoid generated by the LFOs is of the
formula Asin(nF/M) or Acos(nF/M), where
nisthetimeindex,F/M=2
πf/FS,Misthe
maximum internal value, f is the selected
frequency, and FSis the sampling
frequency. Thus the frequency extrema
are: f=(F/M)F
S
/(2π)
fmin = (0x1/0x3ffff) (48kHz)/(2π)
= 0.029Hz
fmax = (0x1fff/0x3ffff) (48kHz)/(2π)
= 239Hz
Triangle waves are generated by incremen-
tally adding or subtracting 0x400000*F/M
(= 222*F/M) from the maximum internal
negative or positive value respectively. Its
frequency extrema are then:
f=#Samples/#Steps
=F
S/ (4 Max/Increment)
=F
S/ (4 0x7fffff/(222*F/M))
fmin = 48kHz / (8/(0x1/0x3ffff))
= 0.023Hz
fmax = 48kHz / (8/(0x1fff/0x3ffff))
= 187Hz
When chorus instructions are used,
addresses are offset by the output an LFO.
The range of this offset is plus and minus
A/8 samples, or A/4 samples total.
Following the 4 LFO coefficient words are
124 MAC instruction words. These
instructions allow the manipulation of the
DRAM and the waveforms generated by
the LFOs.
A good NOP instruction is 0x00030000.
This instruction preserves the value in all
registers, and is the NOP executed in the
MAC during the first four ticks of every
sample period while the LFO coefficients
are loaded.
By judiciously choosing the LFO frequency
and waveform with which to sweep
throughtheDRAM,itispossibleto
generate pitch shifts, flanges, choruses,
reverbs, and other effects. Please see
application notes for descriptions and
examples.
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MAC Instruction Word
Bit # Description
31 S: Sign bit for multiplier coefficient.
C[7:1]: Multiplier coefficient, 2’s complement.
C[7:0]: Chorus instruction. Only the 7 MSBs
are used as multiplier coefficients. The LSB is
used in chorus mode. If I[5] is set, C[7:0] is:
CDescription
7
Chorus/Xfade select:
1: Pass LFO address to address
generator & select chorus coefficient.
0: Mask LFO address to address
generator & select crossfade coefficient.
61’s complement the LFO address sign
bit. 1
5 1’s complement the LFO coefficient.
4 1’s complement the LFO address.
3LFO latch. 1: Latch in new LFO data;
0: Hold last LFO data. 2
2:1 LFO select.
30:23
0 LFO sine/cosine select. 1: Cos; 0: Sin.
22 W: Write select. 3, 4
I[5:0]: Instruction field.
IDescription
5
Chorus select (When set, MAC
coefficient is LFO block output, LFO
address offset added to DRAM
address).
4 Clock register C. 3
3 Clock register B. 5
2 Reserved – set to zero.
I[1:0] Instruction
11 Acc = Prod + Acc 6
10 Acc = Prod + C 3
01 Acc = Prod + B 5
21:16
1:0
MAC
product
instruc-
tion. 00 Acc = Prod + 0
15:0
A[15:0]: Multiplicand address. 7, 8 (Currently
only lower 15 bits used; reserve MSB for
future expansion.)
Address 0x0000 = LeftIn/Out;
Address 0x0001 = RightIn/Out.
Notes:
1. This complement is only for the MSB, and sign-
extension bits are not affected.
2. Upon latching new data, the LFO registers will
storethelowerorupperLFOpairs’
sinusoid/triangle waves, and the lower or upper
LFO pairs’ crossfade coefficient. I.e. there are
two pairs of registers; LFO 0/1’s sinusoid
/triangle/crossfade will be latched together, and
LFO 2/3’s sinusoid/triangle/crossfade will be
latched together.
3. The LeftOut, RightOut, and C registers are in
parallel with the accumulator, and will contain
thesamevalueastheaccumulatorifclockedat
the end of the tick. Thus, a write to LeftOut or
RightOut will store the current tick’s results.
4. A write to DRAM stores the last tick’s results into
address A. During writes, the multiplicand is set
to be the Acc, since A[15:0] is used for the
destination address. Writes to LeftOut or
RightOut can use the Acc = Product + Acc
instruction with the multiplier coefficient set to 0
to pass all bits unaltered.
5. Register B, if clocked at the end of the tick, will
store the value of the current tick’s multiplicand.
When a read is executed, B latches LeftIn,
RightIn, or DRAM. When a write is executed, B
latches the accumulator from the last tick.
6. The accumulator contains the result from the
last instruction tick, and is updated at the end of
the current instruction tick.
7. The internal DRAM address offset automatically
decrements by 1 every word clock period.
8. Because addresses 0x0000 and 0x0001 are
being used to access the left and right channels,
those DRAM memory locations may not be
directly written to or read from.
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Control/Status Word 0
Bit # Description
31:30 Reserved. Set to zero.
29:16 B[13:0]: DRAM read data. 1
15:11 Reserved. Set to zero.
10 O: MAC overflow. Self-clears after read. Read
only.
9 P: Self test pass. Read only.
8R: Ready indication. Read/write/test/clear
complete.
7M: DigOut mute in external mode. Resets
to 1.
6Z: DRAM zero. Initiates zeroing cycles until
deasserted. Resets to 0. 2, 3, 4, 5, 6
5X: DRAM zero cancel. Prevents zeroing
circuitry from running until deasserted.
Overrides Z. Resets to 0. 3
4L: LFO reset pulse. Resets LFO internal
status registers and clears overflow flag. Self
clearing. Resets to 0.
3
I: Instruction RAM direct mode. Resets to 1.
1: Instructions are written/read as soon as
received; 0: Instructions are written/read
when the address counter rolls around to
matching address. 7
2 Reserved. Set to zero.
1S[1]: DRAM self test pattern select.
1: Load DRAM with 2AAA/1555 checkerboard;
0: Load DRAM with 1555/2AAA checkerboard.
0S[0]: DRAM self test initiate. Self-clears after
test completion. Resets to 0. 2, 3, 6, 8, 9
Notes:
1. The floating point format used in the DRAM is:
E[2:0].S.F[9:0], where E is the exponent, S is the
sign bit, and F is the fractional portion. The
expansion of the floating point into fixed point is
as follows:
If E<7, S E*S !S FFFFFFFFFF (8-E)*0
(where E*S means E number of S bits).
If E=7, S SSSSSSS FFFFFFFFFF 00.
This method encodes one extra bit for sign
extensions less than 7 bits.
2. The DRAM zeroing circuitry and DRAM self test
circuitry share gates; do not turn more than one
on at a time.
3. The DRAM zeroing cycle will run to completion
even if Z deasserted. Only the X bit may cancel
it mid-cycle. Until the cycle ends, self test
results will be inaccurate. Thus do not deassert
Z and assert S[0] at the same time. Rather,
assert X and S[0] at the same time.
Note that Z does not self-clear, and will affect
both internal and external mode.
4. After a DRAM zeroing cycle has completed, do
not start another for one word clock period.
5. A DRAM zeroing cycle takes approximately
5.33ms to complete with a 12MHz crystal.
6. During DRAM zeroing and test cycles, reads and
writes to the DRAM are ignored.
7. For dynamically changing programs, deassert I
so that changing the program does not interrupt
its execution. Otherwise reads and writes to the
Instruction RAM will usurp the address bus to
the RAM and cause address jumps in the
instruction sequence. With I deasserted, reads
and writes to each address may take up to one
word clock period to complete. Thus during
continuous writes, the start of each instruction
word should be at least one word clock period
apart, and during reads the serial clock should
wait1wordclockaftertheaddressbefore
continuing.
8. The DRAM self test cycle will run to completion
even if S[0] is deasserted. It may not be
cancelled.
9. A DRAM self test cycle takes approximately
10.66ms to complete with a 12MHz crystal.
Control/Status Word 1
Bit # Description
31
R: Read select. Read data from DRAM
address A[15:0] and put data in B of
control/status word 0. Self-clears after
completion.
30 W: Write select. Write data D[13:0] to DRAM
address A[15:0]. Self-clears after completion.
29:16 D[13:0]: DRAM write data.
15:0 A[15:0]: DRAM address. The MSB is unused
and reserved for future expansion.
Note:
Reading and writing DRAM will usurp DRAM access
for one cycle, possibly disrupting proper code
execution.
Other notes:
1. When in internal mode, program changes will
start a DRAM zero cycle.
2. Resets always start a DRAM zero cycle.
3. To meet refresh requirements below 70 °C,
access each address (modulo 1024) every 1.34
ms. If program code does not do this, then (at 48
kHz) read 16 locations each cycle spaced
1024/16 = 64 addresses apart, to meet refresh
requirements. (For instance, addresses 0x0002,
0x0042, ..., 0x03C2.)
4. ROMs may not be read due to the serial interface
becoming the program select interface when in
internal mode.
5. Use of Reset is mandatory to obtain proper
operation of the AL3201.
The 4 word formats: LFO, MAC, CS0, CS1
LFO: PSXXFFFF FFFFFFFF FAAAAAAA AAAAAAAA
MAC: SCCCCCCC CWIIIIII AAAAAAAA AAAAAAAA
CS0: --BBBBBB BBBBBBBB -----OPR MZXLI-SS
CS1: RWDDDDDD DDDDDDDD AAAAAAAA AAAAAAAA
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DS3201-0402 12555 Jefferson Blvd., Suite 285
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Phone (310) 301-0780 Fax (310) 306-1551 www.alesis-semi.com
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Serial Interface Format
The basic format for the micro serial interface is:
Attn Sel R/W A7 A6 A5 A4 A3 A2 A1 A0 DN DN-1 DN-2 … D2 D1 D0 Attn Desel
ßß
Attn: A 0-1-0 is used to signal attention/start. Writemodeonly
Sel/Desel: 0:Select; 1:Deselect. A7 - A0: Address
R/W: 0:Read; 1:Write DN - D0: Data
Notes:
1. There is a short period of High-Z during a read
between A0 and the first data bit shifted out.
This period must be at least 5 system clocks
long, 1 word clock long if not in direct mode
(CS0[3]).
2. As long as data is being sent during a write, the
address will be automatically incremented.
Therefore only a start address need be sent.
3. The phase of the clock is unimportant.
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DigIn/DigOut Interface Format
Suggested Connections
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NOTICE
Alesis Semiconductor reserves the right to make changes to their products or to discontinue
any product or service without notice. All products are sold subject to terms and conditions
of sale supplied at the time of order acknowledgement. Alesis Semiconductor assumes no
responsibility for the use of any circuits described herein, conveys no license under any
patent or other right, and makes no representation that the circuits are free of patent
infringement. Information contained herein are only for illustration purposes and may vary
depending upon a user’s specific application. While the information in this publication has
been carefully checked, no responsibility is assumed for inaccuracies.
Alesis Semiconductor products are not designed for use in applications which involve
potential risks of death, personal injury, or severe property or environmental damage or life
support applications where the failure or malfunction of the product can reasonably be
expected to cause failure of the life support system or to significantly affect its safety or
effectiveness.
All trademarks and registered trademarks are property of their respective owners.
Contact Information:
Alesis Semiconductor
12555 Jefferson Blvd., Suite 285
Los Angeles, CA 90066
Phone: (310) 301-0780
Fax: (310) 306-1551
Email: sales@alesis-semi.com
Copyright 2003 Alesis Semiconductor
Datasheet March 2003
Reproduction, in part or in whole, without the prior written consent of Alesis
Semiconductor is prohibited.
