Input/Output Of Data Bytes And Bits - Keysight VXI Bus 75000 C Series User And Programming Manual

Using the Keysight E1458A Digital I/O Module

Input/Output of Data Bytes and Bits

Data input is performed using commands in the SCPI MEASure:DIGital
subsystem. Data output is performed using the commands in SCPI
[SOURce:]DIGital subsystem.
The returned value of an input, or the TTL levels of an output, will depend upon
the POLarity programmed for the port.
Both input and output operations will attempt to complete the handshake mode
set for the port and may "hang" if required handshake operations are not
completed.
Input
Input operations can involve single bits, 8-bit bytes, or multiple bytes. Single-bit
input operations always return a decimal value of 0 or 1. Byte or multiple-byte
input operations always return numbers in decimal format.
Bit Input
The SCPI command for inputting the state of a single bit on a data port is:
This command instructs the Keysight E1458A Digital I/O Module to return a
value of either 0 or 1, indicating the condition of bit m on port n, following
completion of the input handshake. The value returned depends upon the
programmed state of the port POLarity. In the default state (POSitive polarity) a
TTL High on the data line specified by m will return a 1. For example, the
following BASIC program code will request and display the state of data line 3
(bit-3) on port 4.
Bit numbers range from 0 to 7 for single-port operations. For multiple-port
operations, bit numbers can range from 0 to 95. The section "Multiple-Port
Operations" later in this chapter describes bit numbering for multiple-port
operations. For a single port, the data lines number and bit numbers correspond:
42
MEASure:DIGital:DATAn[:type]:BITm?
120 OUTPUT @Dio;"MEAS:DIG:DATA4:BIT3?"
130 ENTER @Dio;Bits
140 DISP "State of bit 3 on port 4" ;Bits
Dn_7 Dn_6 Dn_5
Bit 7 Bit 6 Bit 5
Input/Output of Data Bytes and Bits
Dn_4 Dn_3 Dn_2
Bit 4 Bit 3 Bit 2
Keysight E1458A 96-Channel Digital I/O Module User Guide
Dn_1 Dn_0
Bit 1 Bit 0