ADS1291IRSMT datasheet(49/83 Pages) TI2

49 / 83 page

Hi-Z

START

DRDY

SCLK

DIN

DOUT

RDATA Opcode

STATUS Word + Channel Data (up to 72 bits)

RDATA Opcode

ADS1291, ADS1292, ADS1292R

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SBAS502C – DECEMBER 2011 – REVISED APRIL 2020

Product Folder Links: ADS1291 ADS1292 ADS1292R

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8.5.2.8 SDATAC: Stop Read Data Continuous

This opcode cancels the Read Data Continuous mode. There is no restriction on the SCLK rate for this

command, but the following command must wait for 4 tCLK cycles.

8.5.2.9 RDATA: Read Data

Issue this command after DRDY goes low to read the conversion result (in Stop Read Data Continuous mode).

There is no restriction on the SCLK rate for this command, and there is no wait time needed for the subsequent

commands or data retrieval SCLKs. To retrieve data from the device after RDATA command is issued, make

sure either the START pin is high or the START command is issued. When reading data with the RDATA

command, the read operation can overlap the occurrence of the next DRDY without data corruption. Figure 53

shows the recommended way to use the RDATA command. RDATA is best suited for ECG- and EEG-type

systems where register setting must be read or changed often between conversion cycles.

Figure 53. RDATA Usage

8.5.2.10 Sending Multi-Byte Commands

The ADS1291, ADS1292, and ADS1292R serial interface decodes commands in bytes and requires 4 tCLK cycles

to decode and execute. Therefore, when sending multi-byte commands, a 4 tCLK period must separate the end of

one byte (or opcode) and the next.

Assume CLK is 512 kHz, then tSDECODE (4 tCLK) is 7.8125 µs. When SCLK is 16 MHz, one byte can be

transferred in 500 ns. This byte-transfer time does not meet the tSDECODE specification; therefore, a delay must be

inserted so the end of the second byte arrives 7.3125 µs later. If SCLK is 1 MHz, one byte is transferred in 8 µs.

Because this transfer time exceeds the tSDECODE specification, the processor can send subsequent bytes without

delay. In this later scenario, the serial port can be programmed to move from single-byte transfer per cycle to

multiple bytes.

ADS1291IRSMT Datasheet(PDF) 49 Page - Texas Instruments