AK7750 Datasheet, PDF (66/77 Pages) Asahi Kasei Microsystems – Audio DSP with Built-in Hands-Free Phone Features

[ASAHI KASEI]
[AK7750]
5 ) Simplified Write Error Check
The AK7750 can easily check whether any error exists in the write data, using Cyclic Codes.
(Note: the main purpose of this is to check erroneous writes due to induced noise etc. caused between
microprocessor and DSP. As this is a CRC-based (cyclic redundancy check ) check, and as input data is
checked before it is written into RAM and register, it does not guarantee 100 % write error detection ).
Here definitions are made as follows :
y serial data D (x) : SI data being input during the time from RQ
y Generator Polynomial G(x)=x¹⁶+x¹²+x⁵+1 (default value = 0)
y remainder R (x), when D(X) is divided by G (x)
to fall to RQ
to rise.
In order to perform a simplified write error check, perform the following:
1) Transfer serial data D(x) to be checked.
2) Write the remainder R(x) of serial data D(x) to register, using command code B6h.
3) Read out R(x) using command code D6h to check if it is correctly written (CRC check function operates
even when no read is performed).
4) If the remainder of the serial data D(x) divided by G(x) is equal to R(x), SO outputs “H” at the rising
edge of RQ until the following rising edge of RQ occurs for next serial data-write. When the SO
output is used, as in the case of a read in RUN mode, there is a conflict. Therefore when a CRC check
is done, do not execute read operation in RUN mode until the check is completed). If it is not equal to
R(x), “L” is output.
5) If other serial data is to be checked, repeat 1 ) ~ 4 ) above.
„ Details of Data Transfer Procedure
1) Write the register
Writing remainder data R(x) is executed in 3 bytes/set data (24-bit).
Data translate order.
cCommand code
dUpper 8bit of R(x)
eLower 8bit of R(x)
B6h
(D15 * * * * * * D8)
( D7 * * * * * * D0)
2) Read out the register
Reading remainder data R(x) is executed in 3 bytes/set data (24-bit).
Data translate order
cCommand code
dUpper 8bit of R(x)
eLower 8bit of R(x)
D6h
(D15 * * * * * * D8)
( D7 * * * * * * D0)
R(x)
RQ
SCLK
SI
SO
B6h
D15 *** D
D6h
D15 *** D
Example: Control register writing, reading
[MS0296-E-00]
66
2005/03