AD7321

Data Sheet

Rev. B | Page 22 of 36

REGISTERS

The AD7321 has two programmable registers: the control register and the range register. These registers are write only registers.

ADDRESSING REGISTERS

A serial transfer on the AD7321 consists of 16 SCLK cycles. The three MSBs on the DIN line during the 16 SCLK transfer are decoded to

determine which register is addressed. The three MSBs consist of the write bit, a ZERO bit, and the register select bit. The register select

bit is used to determine which of the two on-board registers is selected. The write bit determines if the data on the DIN line following the

register select bit loads into the addressed register. If the write bit is 1, the bits load into the register addressed by the register select bit. If

the write bit is 0, the data on the DIN line does not load into any register.

Combinations of the write bit, the ZERO bit, and the register select bit other than those specified in Table 8 access registers for Analog

Devices internal use only. Do not access these registers, as doing so may lead to unspecified operation of the device.

Table 8. Decoding Register Select Bits and Write Bit

Write

ZERO

Register Select

Description

0

0

0

Data on the DIN line during this serial transfer is ignored.

1

0

0

This combination selects the control register. The subsequent 12 bits are loaded into

the control register.

1

0

1

This combination selects the range register. The subsequent 6 bits are loaded into the

range register.