Datasheet

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REV. A

AD7719

–19–

CR7 CR6 CR5 CR4 CR3 CR2 CR1 CR0

WEN

(0) R/

(0) 0 (0) 0 (0) A3 (0) A2 (0) A1 (0) A0 (0)

Table IX. Communications Register Bit Designations

Bit Bit

Location Name Description

CR7 WEN Write Enable Bit. A 0 must be written to this bit so the write operation to the Communications register

actually takes place. If a 1 is written to this bit, the part will not clock on to subsequent bits in the register.

It will stay at this bit location until a 0 is written to this bit. Once a 0 is written to the WEN bit, the next

seven bits will be loaded to the Communications register.

CR6 R/W A 0 in this bit location indicates that the next operation will be a write to a specified register. A 1 in this

position indicates that the next operation will be a read from the designated register.

CR5 Zero A 0 must be written to this bit position to ensure correct operation of the AD7719.

CR4 Zero A 0 must be written to this bit position to ensure correct operation of the AD7719.

CR3–CR0 A3–A0 Register Address Bits. These address bits are used to select which of the AD7719’s registers is being

accessed during this serial interface communication. A3 is the MSB of the three selection bits.

Communications Register (A3, A2, A1, A0 = 0, 0, 2, 0)

The Communications register is an 8-bit write-only register. All

communications to the part must start with a write operation to

the Communications register. The data written to the Commu-

nications register determines whether the next operation is a read

or write operation, and to which register this operation takes

place. For read or write operations, once the subsequent read or

write operation to the selected register is complete, the interface

returns to where it expects a write operation to the Communications

or after a RESET, the AD7719 is in this default state waiting for a

write operation to the Communications register. In situations where

the interface sequence is lost, a write operation of at least 32 serial

clock cycles with DIN high returns the AD7719 to this default

state by resetting the part. Table IX outlines the bit designations

for the Communications register. CR0 through CR7 indicate the

bit location, with CR denoting that the bits are in the Commu-

nications register. CR7 denotes the first bit of the data stream.

Table X. Register Selection Table

A3 A2 A1 A0 Register

0000Communications Register during a Write Operation

0000Status Register during a Read Operation

0001Mode Register

0010Main ADC Control Register (AD0CON)

0011Aux ADC Control Register (AD1CON)

0100Filter Register

0101Main ADC Data Register

0110Aux ADC Data Register

0111I/O Control Register

1000Main ADC Offset Calibration Register

1001Aux ADC Offset Calibration Register

1010Main ADC Gain Calibration Register

1011Aux ADC Gain Calibration Register

1100Test 1 Register

1101Test 2 Register

1110Undefined

1111ID Register