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200 L4400 User’s Guide
8 L4450A 64-Bit Digital I/O with Memory and Counter
Basic Digital I/O Operations
Channel Numbering and Width
The digital channels are numbered by bank; 101 through 104 and 201 through
204 for banks 1 and 2 respectively.
Using SCPI commands you can group digital I/O channels together to allow 16-
or 32- bit operations. The first and third channels on a bank can be control
channels. Width and direction of the memory operations are controlled by the
width and direction of the first channel on the bank (i.e., 101 or 201). In the
SCPI language for the L4450A, BYTE refers to 8-bit operations, WORD refers to
16- bit operations, and LWORd refers to 32-bit operations.
This diagram illustrates how the channels are numbered for each
configuration.
Reading Digital Data
The simplest way to read a digital channel is using the MEASure:DIGital?
query. This query sets the channel to be an input channel and sets all other
channel parameters to the default settings.
For example, sending the following SCPI command to the L4450A will read the
value of the 8- bit channel 102. An unsigned integer value is returned that
represents the state of the 8 bits on channel 102.
MEAS:DIG? BYTE, (@1102)
By adding parameters to the command, you can set the channel width,
threshold, and polarity for read. For example, sending the following SCPI
command you can read the 32- bit channel 201.
MEAS:DIG? LWOR, 2.5, NORM, (@1201)
Bank 1 Bank 2
Channel
BYTE (default) 101 102 103 104 201 202 203 204
8-bits 8-bits 8-bits 8-bits 8-bits 8-bits 8-bits 8-bits
WORD 101 103 201 203
16-bits 16-bits 16-bits 16-bits
LWORd 101 201
32-bits 32-bits