Datasheet

START
DRDY
CS
SCLK
DIN
DOUT
Hi-Z
RDATAC Opcode
Status Register + n-Channel Data
Next Data
t
UPDATE
(1)
ADS131E04
ADS131E06
ADS131E08
SBAS561A –JUNE 2012–REVISED APRIL 2013 www.ti.com
START: Start Conversions
This opcode starts data conversions. Tie the START pin low to control conversions by command. If conversions
are in progress, this command has no effect. The STOP opcode command is used to stop conversions. If the
START command is immediately followed by a STOP command, then have a gap of 4 t
CLK
cycles between them.
When the START opcode is sent to the device, keep the START pin low until the STOP command is issued.
(See the START subsection of the SPI Interface section for more details.) There are no SCLK rate restrictions
for this command and it can be issued at any time.
STOP: Stop Conversions
This opcode stops conversions. Tie the START pin low to control conversions by command. When the STOP
command is sent, the conversion in progress completes and further conversions are stopped. If conversions are
already stopped, this command has no effect. There are no SCLK rate restrictions for this command and it
can be issued at any time.
OFFSETCAL: Channel Offset Calibration
This command is used to cancel the channel offset. OFFSETCAL must be executed every time there is a change
in PGA gain settings.
RDATAC: Read Data Continuous
This opcode enables the conversion data output on each DRDY without the need to issue subsequent read data
opcodes. This mode places the conversion data in the output register and may be shifted out directly. The read
data continuous mode is the default mode of the device and the device defaults in this mode on power-up.
RDATAC mode is cancelled by the Stop Read Data Continuous command. If the device is in RDATAC mode, an
SDATAC command must be issued before any other commands can be sent to the device. There are no SCLK
rate restrictions for this command. However, subsequent data retrieval SCLKs or the SDATAC opcode
command should wait at least 4 t
CLK
cycles for the command to execute. RDATAC timing is shown in Figure 39.
As Figure 39 shows, there is a keep out zone of 4 t
CLK
cycles around the DRDY pulse where this command
cannot be issued in. If no data are retrieved from the device, DOUT and DRDY behave similarly in this mode. To
retrieve data from the device after the RDATAC command is issued, make sure either the START pin is high or
the START command is issued. Figure 39 shows the recommended way to use the RDATAC command.
RDATAC is ideally-suited for applications such as data loggers or recorders where registers are set once and do
not need to be reconfigured.
(1) t
UPDATE
= 4 / f
CLK
. Do not read data during this time.
Figure 39. RDATAC Usage
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