Models 2500 and 2502 User’s Manual GPIB 488.1 Protocol G-3
Protocol differences
The following information covers the differences between the 488.1 protocol and the SCPI
protocol.
Message exchange protocol (MEP)
When the 488.1 protocol is selected, the MEP is disabled to speed up GPIB operation.
The following guidelines/limitations must be followed when using the 488.1 protocol:
• If a query is sent, it must be the only command on the line (this limitation also means
no multiple queries can be sent). Otherwise, full SCPI command syntax is still sup-
ported including long-form and short form commands, multiple commands, and MIN/
MAX/DEF parameter definitions.
For example, the following command strings are invalid:
:SOUR2:VOLT:RANG 10;*OPC?
:SENS2:CURR:RANG?;:READ?
:READ?;:READ?
The following command strings are valid:
:SOUR1:VOLTage:STARt 1;STOP 10;step 1
:curr:nplc 1.0;:curr:rang min
:SENS2:CURR:RANG? MAX
:READ?
• When a query is sent, either the data must be read back or a Device Clear (DCL) or
Interface Clear (IFC) must be performed to reset the query.
• When sending a command or query, do not attempt to read data from the Model 2500
until the terminator has been sent (usually Line Feed with EOI). Otherwise, a DCL or
IFC must be sent to reset the input parser.
• When receiving data, all data, up to and including the terminator (LF with EOI), must
be accepted. Otherwise, a DCL or IFC must be sent to reset the output task.
• Empty command strings (terminator only) should not be sent.
Using SCPI-based programs
In general, an existing SCPI-based program will run properly and faster in the 488.1 pro-
tocol as long as it meets the above guidelines and limitations.
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