488 CONTROLLER
18
3.3 Selecting Terminator Substitution
In the Controller and Peripheral Modes, the 488 Controller is not sensitive as to whether CR or LF is used
as a serial input terminator to a command. In general, it requires only one of either to cause command
execution. The IEEE input terminator is fixed to LF. The switches that allow terminator selection, shown in
the following diagrams, set only the serial output and IEEE output terminators for these operation modes.
In the transparent Pass-Thru modes, the 488 Controller can be configured to provide RS-232-to-IEEE 488
and IEEE-488-to-RS-232 terminator substitution. This is useful when interfacing an RS-232 device which only
issues carriage return (CR) as an output terminator to an IEEE controller which expects a carriage return
followed by a line feed (CR-LF).
In the above case, the serial terminator should be selected for CR Only while the IEEE terminator is set to
CR-LF. When a serial CR character is received, it is discarded, and an IEEE CR-LF is substituted for it. In the
IEEE-to-RS-232 direction, the IEEE CR is unconditionally discarded. When it receives the IEEE LF, a serial
CR is substituted.
To make the 488 Controller totally data transparent in the Pass-Thru modes, set both the serial and IEEE
terminators to be CR Only or LF Only.
3.3.1 S
ERIAL
T
ERMINATOR
SW2-3 and SW2-4 select the serial terminators for the serial input (Pass-Thru Modes Only) and output.
The factory default is CR-LF.
Figure 3-10. Switch SW2: Selecting the serial terminator.
Switch
Side
View
DOT
CR Only
1 2 3 4 5 6 7 8
OPEN
LF-CR
1 2 3 4 5 6 7 8
OPEN
1 2 3 4 5 6 7 8
OPEN
LF Only
1 2 3 4 5 6 7 8
OPEN
CR-LF
