AK4955 Datasheet, PDF (77/117 Pages) Asahi Kasei Microsystems – 24bit Stereo CODEC with MIC/SPK/Cap-less VIDEO-AMP/ LDO & DSP

[AK4955]
2. READ Operation
Random address read operation is only supported when accessing the internal DSP.
The random read operation allows the master to access any memory location at random. Prior to issuing the slave address
with the R/W bit “1”, the master must first perform a “dummy” write operation. The master issues a start condition, a
slave address (R/W bit = “0”) and then the register address to read. After the register address is acknowledged, the master
immediately reissues the start condition and the slave address with the R/W bit “1”. The AK4955 then generates an
acknowledge, 1 byte of data and increments the internal address counter by 1. If the master does not generate an
acknowledge but generates a stop condition instead, the AK4955 ceases the transmission.
R/W=0
start
s
SDA
Slave
Address
Command
code
Address
Address
~~~
ACK
ACK
ACK
ACK
Address data is 2byte assignment. No address
input if there is no address.
~~~
R/W=1
start
stop
s
Slave
Address
WAIT
DATA
DATA
~~
ACK _{WAIT 1byte} ACK
Master
ACK
Master
DATA
P
ACK
Master
Data length is variable with the areas to be read.
Figure 69. Random Address Read from DSP
Command
70H
71H
72H
73H
7DH
7FH
7EH
Address Length
None
None
None
None
2byte assignment
2byte assignment
2byte assignment
Data Length
4byte
4byte
4byte
4byte
2byte assignment
×n (n=2~12)
5byte×n
2byte×n
Content
@MICR0 reading
@MICR1 reading
@MICR2 reading
@MICR3 reading
CRAM write preparation data reading during RUN
PRAM reading during a system reset
CRAM reading during a system reset
Note 53. Length of read data is variable by command code. As for access to RAM, it is possible to read data at
sequential address locations by reading data continuously. Reading command codes other than above are
prohibited. There is a wait time (1byte) after an acknowledge following read commands after the dummy
writing. During this wait time, the SDA pin is in output state and the output data is indefinite. MSB data is
output after the first acknowledge following this wait time.
Table 69. List of Usable Read Command Codes in Read Sequence
MS1343-E-00
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2011/12