ak7746 ETC-unknow, ak7746 Datasheet - Page 57

• Manufacturer Part Number: ak7746
• Description: Audio With 5-channel 24-bit Input
• Manufacturer: ETC-unknow

5) Simple error check for communication
The AK7746 has a simple CRC error check function.
(Note: Its main purpose is checking against the noise effects during writes from microprocessor to the AK7746. This check CANNOT
guarantee 100% error detection on the AK7746.
Explanation:
* Specific order of data translates.
1) Write the register
2) Read out the register
[MS0369-E00]
[ASAHI KASEI]
1)
2)
3)
4)
* Serial data(X): Input SI data from RQ fall to rise up.
* Generator polynomial G(x) =x
* The rest of D(x) divides by G(x) is R(x).
In order to do simple error check is as following:
The rest R(x) data writing is using 3-byte/unit (24bit)
The rest R(x) data reading out is 3-byte/unit (24bit)
Note) In the case of detecting CRC error in runtime “CRAM rewrite” (A4h) or “OFRAM rewrite“(94h), the possibility of writing
data to the wrong address exists.
Use the command code B6h and write the R(x) (the rest result of serial data D(x) divided by G(x)).
Then use the command code D6h and read out R(x) to check whether the R(x) is correct or not. (Unless this read out, CRC
check itself works.)
If the result of D(x) divided by G(x) is equal to R(x), SO outputs “H” from the next rising edge of RQ to falling edge of
check.) If R(x) is not equal to the result, it outputs “L”.
If you want to check other serial data, then repeat action form 1) to 3).
RQ . (However, SO read out from micro-controller is prior to this signal. Refrain from a runtime read out while doing CRC
Data translate order
This division is using exclusive-or instead of subtraction during this calculation.
It makes good 16-bit zero data after translated serial data D(X) and the rest R(X) of
this division comes out 16bit data.
Data translate order.
Command code
Upper 8bit of R(x) (D15 * * * * * * D8)
Lower 8bit of R(x) ( D7 * * * * * * D0)
Command code
Upper 8bit of R(x) (D15 * * * * * * D8)
Lower 8bit of R(x) ( D7 * * * * * * D0)
16
+x
12
+x
5
B6h
D6h
+1 (X.25 of CCITT standard order of hexadecimal is 11021h).
- 57 -
[AK7746]
2004/12