ADT7408CCPZ-R2 AD [Analog Devices], ADT7408CCPZ-R2 Datasheet - Page 18

• Manufacturer Part Number: ADT7408CCPZ-R2
• Description: +-2 C Accurate, 12-Bit Digital Temperature Sensor
• Manufacturer: AD [Analog Devices]

ADT7408
SMBUS/I
The data registers in the ADT7408 are selected by the pointer
register. At power-up the pointer register is set to 0x00, the
location for the capability register. The pointer register latches
the last location to which it was set. Each data register falls into
one of the following three types of user accessibility:
A write to the ADT7408 always includes the address byte and
the pointer byte. A write to any register other than the pointer
register requires two data bytes.
Reading data from the ADT7408 occurs in one of the following
two ways:
SDA
SCL
•
•
•
•
•
SCL
(CONTINUED)
SDA
(CONTINUED)
Read only
Write only
Write/Read same address
If the location latched in the pointer register is correct,
then the read simply consists of an address byte,
followed by retrieving the two data bytes.
If the pointer register needs to be set, then an address
byte, pointer byte, repeat start, and another address
byte accomplish a read.
2
START BY
MASTER
C COMMUNICATIONS
A6
1
A5
D15
1
A4
SERIAL BUS ADDRESS BYTE
D14
A3
FRAME 1
Figure 14. Writing to the Address Pointer Register, Followed by Two Bytes of Data
D13
MOST SIGNIFICANT DATA BYTE
A2
D12
A1
FRAME 3
D11
A0
D10
R/W
D9
ACK
TS
BY
9
Rev. 0 | Page 18 of 24
D8
D7
1
ACK
TS
BY
9
D6
The data byte has the most significant bit first. At the end of a
read, the ADT7408 accepts either acknowledge (ACK) or no
acknowledge (NO ACK) from the master. No acknowledge is
typically used as a signal for the slave that the master has read
its last byte. It typically takes the ADT7408 100 ms to measure
the temperature.
Writing Data to a Register
With the exception of the pointer register, all other registers are
16 bits wide, so two bytes of data are written to these registers.
Writing two bytes of data to these registers consists of the serial
bus address, the data register address written to the pointer
register, followed by the two data bytes written to the selected
data register (see Figure 14). If more than the required number
of data bytes is written to a register, then the register ignores
these extra data bytes. To write to a different register, another
start or repeated start is required.
D7
1
D5
D6
D4
POINTER BYTE
FRAME 2
LEAST SIGNIFICAN DATA BYTE
D5
D3
D4
D2
FRAME 4
D3
D1
D2
D0
D1
ACK
BY
TS
9
D0
STOP
BY
MASTER
ACK
BY
TS
9
STOP
BY
MASTER