ADT7320

Preliminary Technical Data

Rev. PrA | Page 18 of 24

SERIAL INTERFACE

ADT7320

GND

SCLK

DOUT

DIN

CT

INT

10kΩ

10kΩ

PULL-UP

0.1µF

MICROCONTROLLER

CS

Figure 15. Typical SPI Interface Connection

The ADT7320 has a 4-wire serial peripheral interface (SPI). The

interface has a data input pin (DIN) for inputting data to the device,

a data output pin (DOUT) for reading data back from the device,

and a data clock pin (SCLK) for clocking data into and out of

the device. A chip select pin (CS) enables or disables the serial

interface. CS is required for correct operation of the interface.

Data is clocked out of the ADT7320 on the negative edge of SCLK,

and data is clocked into the device on the positive edge of SCLK.

SPI COMMAND BYTE

All data transactions on the bus begin with the master taking

CS from high to low and sending out the command byte. This

indicates to the ADT7320 whether the transaction is a read or a

write and provides the address of the register for the data transfer.

Table 15 shows the command byte.

Table 15. Command Byte

C7

C6

C5

C4

C3

C2

C1

C0

0

R/W

Register address

Continuous read

0

0

Bit C7 of the command byte must be set to 0 to successfully begin a

bus transaction. The SPI interface does not work correctly if a 1

is written into this bit.

Bit C6 is the read/write bit; 1 indicates a read, and 0 indicates a write.

Bits[C5:C3] contain the target register address. One register can

be read from or written to per bus transaction.

Bit C2 activates a continuous read mode on the temperature value

register only. When this bit is set, the serial interface is configured

so that the temperature value register can be continuously read.

When the command word is 01010100 (0x54), the contents of

the temperature value register can be read out without requiring

repeated writes to set the address bits. Simply sending 16 SCLK

clocks to the ADT7320 clocks the contents of the temperature

value register onto the DOUT pin.