Datasheet
Data Sheet AD7787
Rev. A | Page 11 of 20
Table 6. Register Selection
RS1 RS0 Register Register Size
0 0 Communications Register during a Write Operation 8-Bit
0 0 Status Register during a Read Operation 8-Bit
0 1 Mode Register 8-Bit
1 0 Filter Register 8-Bit
1
1
Data Register
24-Bit
Table 7. Channel Selection
CH1 CH0 Channel
0 0 AIN1(+) − AIN1(−)
0 1 AIN2
1 0 AIN1(−) − AIN1(−)
1 1 V
DD
Monitor
STATUS REGISTER (RS1, RS0 = 0, 0; POWER-ON/RESET = 0×8C)
The status register is an 8-bit read-only register. To access the ADC status register, the user must write to the communications register,
select the next operation to be a read, and load Bits RS1 and RS0 with 0s. Table 8 outlines the bit designations for the status register. SR0
through SR7 indicate the bit locations, SR denoting the bits are in the status register. SR7 denotes the first bit of the data stream. The
number in the parenthesis indicates the power-on/reset default status of that bit.
SR7 SR6 SR5 SR4 SR3 SR2 SR1 SR0
RDY (1)
ERR (0) 0 (0) 0 (0) 1 (1) 1 (1) CH1 (0) CH0 (0)
Table 8. Status Register Bit Designations
Bit
Location
Bit
Name Description
SR7
RDY Ready Bit for ADC. Cleared when data is written to the ADC data register. The RDY bit is set automatically after the
ADC data register has been read or a period of time before the data register is updated with a new conversion result
to indicate to the user not to read the conversion data. It is also set when the part is placed in power-down mode.
The end of a conversion is indicated by the DOUT/
RDY pin also. This pin can be used as an alternative to the status
register for monitoring the ADC for conversion data.
SR6 ERR
ADC Error Bit. This bit is written to at the same time as the
RDY bit. Set to indicate that the result written to the ADC
data register has been clamped to all 0s or all 1s. Error sources include overrange, underrange. Cleared by a write
operation to start a conversion.
SR5 to
SR4
0 These bits are automatically cleared.
SR3 to
SR2
1 These bits are automatically set.
SR1 to
SR0
CH1 to
CH0
These bits indicate which channel is being converted by the ADC.