ASAHI KASEI
[AK4702EQ]
2. READ Operations
Set R/W bit = “1” for READ operations. 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 the first data word. After the receipt of
each data, the internal address counter is incremented by one, and the next data is taken into next address automatically. If
the address exceeds 08H prior to generating the stop condition, the address counter will “roll over” to 00H and the
previous data will be overwritten.
The AK4702 supports two basic read operations: CURRENT ADDRESS READ and RANDOM READ.
2-1. CURRENT ADDRESS READ
The AK4702 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 with R/W bit set to “1”, the AK4702 generates an
acknowledge, transmits 1byte data which address is set by the internal address counter and increments the internal address
counter by 1. If the master does not generate an acknowledge to the data but generate the stop condition, the AK4702
discontinues transmission
S
S
T
O
P
T
A
R
T
R/W= “1”
Slave
Address
S
Data(n)
Data(n+1)
Data(n+2)
Data(n+x)
P
SDA
A
C
K
A
C
K
A
C
K
A
C
K
A
C
K
A
C
K
Figure 12. CURRENT ADDRESS READ
2-2. 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 a start condition,
slave address(R/W=“0”) and then the register address to read. After the register’s address is acknowledge, the master
immediately reissues the start condition and the slave address with the R/W bit set to “1”. Then the AK4702 generates an
acknowledge, 1-byte data and increments the internal address counter by 1. If the master does not generate an
acknowledge to the data but generate the stop condition, the AK4702 discontinues transmission.
S
T
A
R
T
S
T
A
R
T
S
T
O
P
R/W= “0”
R/W= “1”
Slave
Address
Sub
Address(n)
Slave
Address
S
S
Data(n)
Data(n+1)
Data(n+x)
P
SDA
A
C
K
A
C
K
A
C
K
A
C
K
A
C
K
A
C
K
A
C
K
Figure 13. RANDOM ADDRESS READ
MS0424-E-00
2005/09
- 23 -
AKM [ ASAHI KASEI MICROSYSTEMS ]
