Datasheet

ADS1255

ADS1256

SBAS288K − JUNE 2003 − REVISED SEPTEMBER 2013

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COMMAND DEFINITIONS

The commands summarized in Table 24 control the operation of the ADS1255/6. All of the commands are stand-alone

except for the register reads and writes (RREG, WREG) which require a second command byte plus data. Additional

command and data bytes may be shifted in without delay after the first command byte. The ORDER bit in the STATUS

must stay low during the entire command sequence.

Table 24. Command Definitions

COMMAND DESCRIPTION 1ST COMMAND BYTE 2ND COMMAND BYTE

WAKEUP Completes SYNC and Exits Standby Mode 0000 0000 (00h)

RDATA Read Data 0000 0001 (01h)

RDATAC Read Data Continuously 0000 0011 (03h)

SDATAC Stop Read Data Continuously 0000 1111 (0Fh)

RREG Read from REG rrr 0001 rrrr (1xh) 0000 nnnn

WREG Write to REG rrr 0101 rrrr (5xh) 0000 nnnn

SELFCAL Offset and Gain Self-Calibration 1111 0000 (F0h)

SELFOCAL Offset Self-Calibration 1111 0001 (F1h)

SELFGCAL Gain Self-Calibration 1111 0010 (F2h)

SYSOCAL System Offset Calibration 1111 0011 (F3h)

SYSGCAL System Gain Calibration 1111 0100 (F4h)

SYNC Synchronize the A/D Conversion 1111 1100 (FCh)

STANDBY Begin Standby Mode 1111 1101 (FDh)

RESET Reset to Power-Up Values 1111 1110 (FEh)

WAKEUP Completes SYNC and Exits Standby Mode 1111 1111 (FFh)

NOTE: n = number of registers to be read/written − 1. For example, to read/write three registers, set nnnn = 2 (0010).

r = starting register address for read/write commands.

RDATA: Read Data

Description: Issue this command after DRDY goes low to read a single conversion result. After all 24 bits have been shifted

out on DOUT, DRDY

goes high. It is not necessary to read back all 24 bits, but DRDY will then not return high until new

data is being updated. See the Timing Characteristics for the required delay between the end of the RDATA command and

the beginning of shifting data on DOUT: t

DOUT

SCLK

DIN

MSB

Mid−Byte LSB

DRDY

0000 0001

••• •••

Figure 30. RDATA Command Sequence