[AK4438]
(2)-2. READ Operations
Set the R/W bit = “1” for the READ operation of the AK4438. 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 “14H” prior to generating stop condition, the address counter will “roll over” to “00H” and the data
of “00H” will be read out.
The AK4438 supports two basic read operations: Current Address Read and Random Address Read.
(2)-2-1. Current Address Read
The AK4438 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 “1”, the AK4438 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 AK4438 ceases 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
M
A
S
T
E
R
M
A
S
T
E
R
M
A
S
T
E
R
M
A
S
T
E
R
M
A
S
T
E
R
A
C
K
A
C
K
A
C
K
A
C
K
A
C
K
N
A
C
K
Figure 42. Current Address Read
(2)-2-2. Random Address Read
The random read operation allows the master to access any memory location at random. Prior to issuing
a slave address with the R/W bit =“1”, the master must execute a “dummy” write operation first. 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 AK4438 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 AK4438 ceases 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
M
A
S
T
E
R
M
A
S
T
E
R
M
A
S
T
E
R
M
A
S
T
E
R
A
C
K
A
C
K
A
C
K
A
C
K
A
C
K
A
C
K
N
A
C
K
Figure 43. Random Address Read
016001925-E-00
2016/03
- 50 -
AKM [ ASAHI KASEI MICROSYSTEMS ]
