Datasheet

Hi-Z
START
DRDY
CS
SCLK
DIN
DOUT
RDATAOpcode
Status Register+8-ChannelData(216Bits)
RDATAOpcode
ADS1294, ADS1294R
ADS1296, ADS1296R
ADS1298, ADS1298R
SBAS459I –JANUARY 2010–REVISED JANUARY 2012 www.ti.com
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 48
shows the recommended way to use the RDATA command. RDATA is best suited for ECG- and EEG-type
systems where register settings must be read or changed often between conversion cycles.
Figure 48. RDATA Usage
Sending Multi-Byte Commands
The ADS129x serial interface decodes commands in bytes and requires 4 t
CLK
cycles to decode and execute.
Therefore, when sending multi-byte commands, a 4 t
CLK
period must separate the end of one byte (or opcode)
and the next.
Assume CLK is 2.048MHz, then t
SDECODE
(4 t
CLK
) is 1.96µs. When SCLK is 16MHz, one byte can be transferred
in 500ns. This byte transfer time does not meet the t
SDECODE
specification; therefore, a delay must be inserted so
the end of the second byte arrives 1.46µs later. If SCLK is 4MHz, one byte is transferred in 2µs. Because this
transfer time exceeds the t
SDECODE
specification, the processor can send subsequent bytes without delay. In this
later scenario, the serial port can be programmed to cease single-byte transfer per cycle to multiple bytes.
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Product Folder Link(s): ADS1294 ADS1294R ADS1296 ADS1296R ADS1298 ADS1298R