Datasheet

ADT7408
Rev. 0 | Page 19 of 24
Reading Data From the ADT7408
Reading data from the ADT7408 can take place in one of the
following two ways:
Writing to the Pointer Register for a Subsequent Read
To read data from a particular register, the pointer register must
contain the address of the data register. If it does not, the
correct address must be written to the address pointer register
by performing a single-byte write operation (see
Figure 15).
The write operation consists of the serial bus address followed
by the pointer byte. No data is written to any of the data
registers. Because the location latched in the pointer register is
correct, then the read consists of an address byte, followed by
retrieving the two data bytes (see
Figure 16).
Reading from Any Pointer Register
On the other hand, if the pointer register needs to be set, then
an address byte, pointer byte, repeat start, and another address
byte accomplish a read (see
Figure 17).
SCL
S
D
A
A6 A4A5 A3 A1A2 A0 D7 D5D6 D4 D2D3 D1 D0
9911
FRAME 1
SERIAL BUS ADDRESS BYTE
FRAME 2
POINTER BYTE
ACK
BY
TS
ACK
BY
TS
STOP
BY
MASTER
START
BY MASTER
05716-010
R/W
Figure 15. Writing to the Address Pointer Register to Select a Register for a Subsequent Read Operation
D7 D5D6 D4 D2D3 D1 D0
91
FRAME 3
LEAST SIGNIFICANT DATA BYTE
NO ACK
BY
MASTER
SCL
(CONTINUED)
SDA
(CONTINUED)
SCL
S
D
A
STOP
BY
MASTER
A6 A4A5 A3 A1A2 A0 R/W D15 D13D14 D12 D10D11 D9 D8
9911
FRAME 1
SERIAL BUS ADDRESS BYTE
FRAME 2
MOST SIGNIFICANT DATA BYTE
ACK
BY
TS
START
BY
MASTER
ACK
BY
MASTER
05716-011
Figure 16. Reading Back Data from the Register with the Preset Pointer