AK7712A-VT Datasheet, PDF (39/87 Pages) Asahi Kasei Microsystems – Built-in 20-bit ADC/DAC Sophisticated Audio DSP

ASAHI KASEI
[AK7712A-VT]
„ Coefficient RAM(CRAM)
This is a RAM to store coefficient data for such as digital filter, and can be written the data through CBUS/DBUS. 3
ways are prepared for writing. The first way is to be loaded from such as microcomputer at reset of this LSI. The
second way is to write the 16 data written on microcomputer buffer at running state. The last way is writing from
DBUS, that is controlled by appointing at DST field. Output can be done to multiplier directly or to DBUS(lower 8 bits
are "0" ). The capacity of memory is 256 word × 16-bit. Two pointers are prepared. CP0 is reset to the
address"0(HEX)" and CP1 is reset to "80(HEX)" every sampling cycle, and appointment of pointer is set to CP0. The
address is able to increment(+1) and to decrement(-1). By load command, it is able to load the DBUS data directly
as pointer value. CPC command not only change the pointer but also does increment of the pointer change from.
For example, in the case of changing the pointer from CP0 to CP1, the change CP0 → CP1 and increment of
address of CP0 are done. The timing is shown below.
<List of CRAM Relational Command>
CPC: Pointer change(CP0 → CP1, CP0+1 ; CP1 → CP0, CP1+1)
CPU: Increment of address(+1)
CPD: Decrement of address(-1)
CRAM: Output the data to DBUS
@CP0: Load the data to CRAM-CP0 pointer (for address)
@CP1: Load the data to CRAM-CP1 pointer (for address)
@CRAM: Write DBUS data
It is explained below how those timing go in actual program.
,OP,
,,CPU,,,
,
;be able to output to DBUS and multiplier(CR) 2 steps after
,OP,
,, ,,,
,
;
,OP,CR*DR ,,CPU,,,CRAM,
;
,OP,
,, ,,,TMP0 , @CRAM ;write the data of TMP0 to the address made 1step before by CPU
,OP,CR*DR ,, ,,,
,
;output the data written 1step before by @CRAM to CR and DBUS
,OP,
,,CPC,,,
,
;
,OP,
,, ,,,
,
;
,OP,
,, ,,,
,
;output the data of pointer changed 2 steps before by CRC
,OP,
,, ,,,
,
;operate with the changed pointer until next CPC is executed
0180-E-02
- 39 -
1997/12