AK7755EN_16 Datasheet, PDF (94/109 Pages) Asahi Kasei Microsystems – DSP with Mono ADC Stereo CODEC + Mic/Lineout Amp

[AK7755]
■ Simple Write Error Check
RAM and register data can be checked by cyclic redundancy check (CRC). It realizes a simple error
check of a written data.
1. Checked Data
1-1. SPI Interface
The serial input data of the AK7755 can be checked from a falling edge of the CSN signal to rising
edge of the CSN signal.
· Serial Data D (x): Input data from a falling edge to a rising edge of the CSN.
· Generating Polynomial: G(x)=x¹⁶+x¹²+x⁵+1 (default=0)
· R(x) is defined as the remainder when D(x) is divided by G(x).
CSN
SCLK
SI ^{don’tcare} Command Code (8bit)
(L/H)
1-2. I²C Interface
Address (16bit or 0bit)
Data (write)
X (L/H)
The data after second byte: command code, address and data are checked. (Acknowledge is not
included in the checked data. Therefore, if the command code, address and data are the same as when
SPI interface is used, the CRC error result will also be the same.) The first byte which includes slave
address is excluded. The first byte can be checked with Acknowledge.
· Serial Data D(x): Command Code, Address and Data (Expect slave address)
· Generating Polynomial: G(x)=x¹⁶+x¹²+x⁵+1 (default=0)
· R (x) is defined as the remainder when D(x) is divided by G(x).
2. Simple Write Error Check Sequence
There are two ways to execute a simple write error check.
2-1. CRC Result Reading
(1) Write serial data D(x) that need to be checked.
(2) Read CRC result (the remainder R(x)) by the command code 72h.
(3) Check the result by a microcomputer.
(4) Repeat (1) ~ (3) when checking another serial data.
Note 55. The internal CRC result is not reflected by the command code
2-2. Checking by the STO pin
(1) Set control register CRCE bit to “1”.
(2) Write serial data D(x) that need to be checked.
(3) Write the remainder R(x) of D(x) ti registers by the command code F2H.
(4) The SDO pin outputs “H” when the calculated remainder of D(x) divided by G(x) equals to the
R(x) value. If not, the STO pin outputs “L”.
(5) Repeat (2) ~ (4) when checking another serial data.
Note 56. The STO pin keeps “L” output until an appropriate remainder R(x) is written to the registers.
014006643-E-00
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2014/10