EVAL-ADT7X20EBZ View Datasheet(PDF) - Analog Devices
Part Name
Description
MFG CO.
'EVAL-ADT7X20EBZ' PDF : 24 Pages View PDF
Preliminary Technical Data
ADT7420
READING DATA
Reading data from the ADT7420 is done in a single data byte
operation for the configuration register, the status register,
the THYST register, and the ID register. A two data byte read
operation is needed for the temperature value register, THIGH
setpoint register, TLOW setpoint register, and the TCRIT setpoint
register. Reading back the contents of an 8-bit register similar
to the configuration register is shown in Figure 16. Reading
back the contents of the temperature value register is shown
in Figure 17.
Reading back from any register first requires a single-byte write
operation to the address pointer register to set up the address of
the register that is going to be read from. In the case of reading
back from the 2-byte registers, the address pointer automatically
increments from the MSB register address to the LSB register
address.
To read from another register, execute another write to the
address pointer register to set up the relevant register address.
Thus, block reads are not possible, that is, there is no I2C address
pointer autoincrement except when reading back from a 16-bit
register. If the address pointer register has previously been set
up with the address of the register that is going to receive a read
command, there is no need to repeat a write operation to set up
the register address again.
1
9
SCL
RESET
To reset the ADT7420 without having to reset the entire I2C bus,
an explicit reset command is provided. This uses a particular
address pointer word as a command word to reset the part and
upload all default settings. The ADT7420 does not respond to
the I2C bus commands (do not acknowledge) during the default
values upload for approximately 200 µs.
The reset command address word is 0x2F.
GENERAL CALL
When a master issues a slave address consisting of seven 0s with
the eighth bit (R/W bit) set to 0, this is known as the general call
address. The general call address is for addressing every device
connected to the I2C bus. The ADT7420 acknowledges this address
and reads in the following data byte.
If the second byte is 0x06, the ADT7420 is reset, completely
uploading all default values. The ADT7420 does not respond
to the I2C bus commands (do not acknowledge) while the
default values upload for approximately 200 µs.
The ADT7420 does not acknowledge any other general call
commands.
1
9
SDA
1
0
START BY
MASTER
1
SCL
0
1
0
A1 A0 R/W
P7 P6 P5 P4 P3 P2 P1 P0
FRAME 1
SERIAL BUS ADDRESS
BYTE
ACK. BY
ADT7420
FRAME 2
ADDRESS POINTER REGISTER BYTE
ACK. BY
ADT7420
9
1
9
SDA
1
0
REPEAT START
BY MASTER
0
1
0
A1 A0 R/W
D7 D6 D5 D4 D3 D2 D1 D0
FRAME 3
SERIAL BUS ADDRESS
BYTE
ACK. BY
ADT7420
FRAME 4
DATA BYTE FROM CONFIGURATION
REGISTER
NO ACK. BY STOP BY
MASTER MASTER
Figure 16. Reading Back Data from the Configuration Register
Rev. PrA | Page 19 of
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