Datasheet

ADT7420 Data Sheet
Rev. 0 | Page 18 of 24
WRITING DATA
It is possible to write either a single byte of data or two bytes to
the ADT7420, depending on which registers are to be written.
Writing a single byte of data requires the serial bus address, the
data register address written to the address pointer register,
followed by the data byte written to the selected data register.
This is shown in Figure 14.
For the T
HIGH
setpoint, T
LOW
setpoint, and T
CRIT
setpoint
registers, it is possible to write to both the MSB and the LSB
registers in the same write transaction. Writing two bytes of
data to these registers requires the serial bus address, the data
register address of the MSB register written to the address
pointer register, followed by the two data bytes written to
the selected data register. This is shown in Figure 15.
If more than the required number of data bytes is written to a
register, the register ignores these extra data bytes. To write to
a different register, a start or repeated start is required.
FRAME 1
SERIAL BUS ADDRESS BYTE
FRAME 2
ADDRESS POINTER REGISTER BYTE
ACK. BY
ADT7420
ACK. BY
ADT7420
ACK. BY
ADT7420
STOP BY
MASTER
FRAME 3
DATA BYTE
SDA (CONTINUED)
SCL (CONTINUED)
SCL
SDA
START BY
MASTER
1 0 0 1 0 A1A0 P7P6P5P4P3P2P1P0
9
D7 D6 D5 D4 D3 D2 D1 D0
R/W
191
91
09013-016
Figure 14. Writing to a Register Followed by a Single Byte of Data
FRAME 1
SERIAL BUS ADDRESS BYTE
FRAME 2
ADDRESS POINTER REGISTER BYTE
ACK. BY
ADT7420
ACK. BY
ADT7420
ACK. BY
ADT7420
STOP BY
MASTER
FRAME 4
DATA BYTE
SCL
SDA
START BY
MASTER
1 0 0 1 0 A1A0 P7P6P5P4P3P2P1P0
9
D7 D6 D5 D4 D3 D2 D1 D0
R/W
191
91
ACK. BY
ADT7420
FRAME 3
DATA BYTE
SDA (CONTINUED)
SCL (CONTINUED)
D15 D14 D13 D12 D11 D10 D9 D8
91
09013-017
Figure 15. Writing to a Register Followed by Two Bytes of Data