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SBAS459H

– JANUARY 2010 – REVISED OCTOBER 2011

SPI COMMAND DEFINITIONS

The ADS129x provide flexible configuration control. The opcode commands, summarized in Table 11, control

and configure the operation of the ADS129x. The opcode commands are stand-alone, except for the register

read and register write operations that require a second command byte plus data. CS can be taken high or held

low between opcode commands but must stay low for the entire command operation (especially for multi-byte

commands). System opcode commands and the RDATA command are decoded by the ADS129x on the seventh

falling edge of SCLK. The register read/write opcodes are decoded on the eighth SCLK falling edge. Be sure to

follow SPI timing requirements when pulling CS high after issuing a command.

Table 11. Opcode Command Definitions

COMMAND

DESCRIPTION

FIRST BYTE

SECOND BYTE

System Commands

WAKEUP

Wake-up from standby mode

0000 0010 (02h)

STANDBY

Enter standby mode

0000 0100 (04h)

RESET

Reset the device

0000 0110 (06h)

START

Start/restart (synchronize) conversions

0000 1000 (08h)

STOP

Stop conversion

0000 1010 (0Ah)

Data Read Commands

Enable Read Data Continuous mode.

RDATAC

0001 0000 (10h)

This mode is the default mode at power-up.(1)

SDATAC

Stop Read Data Continuously mode

0001 0001 (11h)

RDATA

Read data by command; supports multiple read back.

0001 0010 (12h)

RREG

Read n nnnn registers starting at address r rrrr

001r rrrr (2xh)(2)

000n nnnn(2)

WREG

Write n nnnn registers starting at address r rrrr

010r rrrr (4xh)(2)

000n nnnn(2)

(1)

When in RDATAC mode, the RREG command is ignored.

(2)

n nnnn = number of registers to be read/written

– 1. For example, to read/write three registers, set n nnnn = 0 (0010). r rrrr = starting

WAKEUP: Exit STANDBY Mode

This opcode exits the low-power standby mode; see the STANDBY: Enter STANDBY Mode subsection of the

SPI Command Definitions section. Time is required when exiting standby mode (see the Electrical

Characteristics for details). There are no restrictions on the SCLK rate for this command and it can be

issued any time. Any subsequent command must be sent after 4 tCLK cycles.

STANDBY: Enter STANDBY Mode

This opcode command enters the low-power standby mode. All parts of the circuit are shut down except for the

reference section. The standby mode power consumption is specified in the Electrical Characteristics. There are

no restrictions on the SCLK rate for this command and it can be issued any time. Send a WAKEUP

command to return device to normal operation. Serial interface is active, thus register read/write commands are

permitted while in this mode.

RESET: Reset Registers to Default Values

This command resets the digital filter cycle and returns all register settings to the respective default values. See

the Reset (RESET) subsection of the SPI Interface section for more details. There are no restrictions on the

SCLK rate for this command and it can be issued any time. 18 tCLK cycles are required to execute the

RESET command. Avoid sending any commands during this time.

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