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L4450A 64-Bit Digital I/O with Memory and Counter 8
L4400 User’s Guide 201
To read digital data with more control over the channel parameters,
use the SCPI CONFigure and SENSe commands. The CONFigure commands set
up the digital I/O channel parameters. For example, sending the following
SCPI command sets 16- bit input channel 103 to use a 2.5 V input threshold,
and normal polarity.
CONF:DIG WORD, 2.5, NORM, (@1103)
Once configured, the data is read using the following command.
SENS:DIG:DATA:WORD? (@1103)
You may also read an individual bit using the SENSe commands.
This allows you to check the state of an individual bit in a channel without
having to create an input mask. For example, the following command returns
the state of bit 3 in the channel 101 byte.
SENS:DIG:DATA:BIT? 3, (@1101)
The acceptable range for the bit parameter is based on the channel width as
shown below:
• BYTE (8- bit): <bit> can range from ‘0’ to ‘7’
• WORD (16- bit): <bit> can range from ‘0’ to ‘15’
• LWORd (32- bit): <bit> can range from ‘0’ to ‘31’
The SENSe command differs from the MEASure command in that it will not
change the direction (input or output) of the channel. If the channel is
configured as an output, the
SENSe command will return the value being
driven.
Writing Digital Data
To write digital data, set the channel output parameters using the SOURce
commands. For example, sending the following SCPI commands to a Digital
I/O module in slot 1 sets a 32-bit channel to use normal polarity,
with active drive and a ‘set’ output voltage of 4 volts.
CONF:DIG:WIDT LWOR,(@1201)
CONF:DIG:POL NORM,(@1201)
SOUR:DIG:DRIV ACT,(@1201)
SOUR:DIG:LEV 4,(@1201)
The width and polarity parameters apply to both input and output operations.