ꢐꢕ ꢙꢚ ꢋ ꢛ ꢛ
ꢐꢕ ꢙꢚ ꢋ ꢛ ꢜ
www.ti.com
SBAS288D − JUNE 2003 − REVISED AUGUST 2004
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
register sets the order of the bits within the output data. CS must stay low during the entire command sequence.
Table 24. Command Definitions
COMMAND
WAKEUP
RDATA
DESCRIPTION
Completes SYNC and Exits Standby Mode
Read Data
1ST COMMAND BYTE
2ND COMMAND BYTE
0000 0000
0000 0001
0000 0011
0000 1111
0001 rrrr
(00h)
(01h)
(03h)
(0Fh)
(1xh)
(5xh)
(F0h)
(F1h)
(F2h)
(F3h)
(F4h)
(FCh)
(FDh)
(FEh)
(FFh)
RDATAC
SDATAC
RREG
Read Data Continuously
Stop Read Data Continuously
Read from REG rrr
0000 nnnn
0000 nnnn
WREG
Write to REG rrr
0101 rrrr
SELFCAL
SELFOCAL
SELFGCAL
SYSOCAL
SYSGCAL
SYNC
Offset and Gain Self-Calibration
Offset Self-Calibration
1111 0000
1111 0001
1111 0010
1111 0011
1111 0100
1111 1100
1111 1101
1111 1110
1111 1111
Gain Self-Calibration
System Offset Calibration
System Gain Calibration
Synchronize the A/D Conversion
Begin Standby Mode
STANDBY
RESET
Reset to Power-Up Values
Completes SYNC and Exits Standby Mode
WAKEUP
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: t6.
DRDY
DIN
0000 0001
DOUT
SCLK
MSB
Mid−Byte
LSB
t6
• • •
• • •
Figure 29. RDATA Command Sequence
34
BB [ BURR-BROWN CORPORATION ]
