AK4145 Datasheet, PDF (19/27 Pages) Asahi Kasei Microsystems – Digital BTSC Stereo Encoder

[AK4145]
3. READ Operations
The AK4145 supports two basic read operations: CURRENT ADDRESS READ and RANDOM READ.
3-1. CURRENT ADDRESS READ
The AK4145 contains an internal address counter that maintains the address of the last word accessed, incremented by
one. Therefore, if the last access (either a read or write) was to address “n”, the next CURRENT READ operation would
access data from the address “n+1”.
After receipt of the slave address when R/W bit set to “1”, the AK4145 generates an acknowledge, transmits 1byte data
which address is set by the internal address counter and increments the internal address counter by 1. The master can read
next address’s data by generating an acknowledge instead of terminating the read cycle after the receipt of the data. If the
address exceeds 05H prior to generating stop condition, the address counter will “roll over” to 00H and the previous data
will be re-read. If the master does not generate an acknowledge but generates stop condition, the AK4145 discontinues
transmission.
SD A
S
T
A
R
S la ve
A ddr ess
T
Data(n)
Dat a(n+1 )
Dat a(n+2 )
S
Data(n+x)
T
O
P
S
P
A
A
A
A
C
C
C
C
K
K
K
K
Figure 14. CURRENT ADDRESS READ
3-2. RANDOM READ
Random read operation allows the master to access any memory location at random. Prior to issuing the slave address
with the R/W bit set to “1”, the master must first perform a “dummy” write operation.
The master issues start condition, slave address(R/W=“0”) and then the register address to read. After the register
address’s acknowledge, the master immediately reissues start condition and the slave address with the R/W bit set to “1”.
Then the AK4145 generates an acknowledge, 1byte data and increments the internal address counter by 1. The master can
read next address’s data by generating the acknowledge instead of terminating read cycle after the receipt of the data. If
the address exceeds 05H prior to generating the stop condition, the address counter will “roll over” to 00H and the
previous data will be re-read. If the master does not generate an acknowledge but generates stop condition, the AK4145
discontinues transmission.
SD A
S
T
A
R
S la ve
A ddress
T
Word
A ddress( n)
S
T
A
R
Slave
Address
T
Data(n)
S
S
A
A
A
C
C
C
K
K
K
Figure 15. RANDOM READ
Data(n+1)
A
A
C
C
K
K
S
Data(n+x)
T
O
P
P
MS0982-E-01
- 19 -
2010/09