AK4955 Datasheet, PDF (71/117 Pages) Asahi Kasei Microsystems – 24bit Stereo CODEC with MIC/SPK/Cap-less VIDEO-AMP/ LDO & DSP

[AK4955]
(2)-2. READ Operations
Set the R/W bit = “1” for the READ operation of the AK4955. After transmission of data, the master can read the next
address’s data by generating an acknowledge instead of terminating the write cycle after the receipt of the first data word.
After receiving each data packet the internal address counter is incremented by one, and the next data is automatically
taken into the next address. If the address exceeds 4FH prior to generating stop condition, the address counter will “roll
over” to 00H and the data of 00H will be read out.
Note 50. Data reading is only available on the following addresses; 00 ~ 4FH and 50H ~ 6FH. When reading address 50H
~ 6FH, the register values are invalid.
The AK4955 supports two basic read operations: CURRENT ADDRESS READ and RANDOM ADDRESS READ.
(2)-2-1. CURRENT ADDRESS READ
The AK4955 has an internal address counter that maintains the address of the last accessed word incremented by one.
Therefore, if the last access (either a read or write) were to address “n”, the next CURRENT READ operation would
access data from the address “n+1”. After receipt of the slave address with R/W bit “1”, the AK4955 generates an
acknowledge, transmits 1-byte of data to the address set by the internal address counter 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.
S
T
A
R/W="1"
R
T
SDA
Slave
S _Address
A
C
K
Data(n)
Data(n+1)
Data(n+2)
MA
MA
MA
AC
AC
AC
S
T
K
S
T
K
S
T
K
E
E
E
R
R
R
Figure 61. Current Address Read
S
T
O
P
Data(n+x)
P
MA
MN
AC
AA
S
T
K
E
S
T
E
C
K
R
R
(2)-2-2. RANDOM ADDRESS READ
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 request, 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 request 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.
S
T
A
R/W="0"
R
T
S
T
A
R/W ="1"
R
T
SDA
Slave
S _Address
Sub
Address(n)
Slave
S _Address
Data(n)
Data(n+1)
A
A
A
MA
MA
C
K
C
K
C
K
AC
S
T
K
A
S
T
C
K
E
E
R
R
Figure 62. Random Address Read
S
T
O
P
Data(n+x)
P
MA
MN
A
S
T
C
K
A
S
T
A
C
E
EK
R
R
MS1343-E-00
- 71 -
2011/12