Measurement Computing DAC488 v.1 - Manual (Page 31)

DAC488 User’s Manual DAC488 Operation 25
For example, a typical configuration may require Port 1 to have all trigger sources disabled, Port 2
configured to trigger on an IEEE Group Execute Trigger, Port 3 to trigger on an external trigger, and Port 4
to trigger on any of the three trigger sources.
The commands to configure the ports for this configuration are shown below:
PRINT#1,"OUTPUT09;G0 Q0 T0 X"
PRINT#1,"OUTPUT09;G2 X"
PRINT#1,"OUTPUT09;Q4 X"
PRINT#1,"OUTPUT09;G8 Q8 T8 X"
•
Line 1: G0 disables all ports from
triggering on an IEEE Group Execute
Trigger,
Q0 disables all ports from
triggering on an external trigger, T0
disables all ports from triggering on a
command trigger (
@ ), and X executes the
commands.
•
Line 2: G2 enables port 2 for triggering
on an IEEE Group Execute Trigger and
X executes the command.
•
Line 3: Q4 enables port 3 for triggering
on an external trigger and X executes the
command.
•
Line 4: G8 enables port 4 for triggering
on an IEEE Group Execute Trigger, Q8
enables port 4 for triggering on an
external trigger,
T8 enables port 4 for
triggering on an a command trigger ( @ ),
and X executes the commands.
After these commands are executed, the
trigger sources will be routed to the ports as
illustrated in the figure.
Trigger Processing & Trigger Overrun
Operation of the DAC488 is controlled by an internal 1 millisecond timer. Each DAC port is updated at a
maximum rate of once every millisecond. When a trigger event occurs, the DAC will output the
programmed voltage within 1 millisecond of receiving the trigger. If a second trigger event occurs before
the DAC has finished processing the first trigger, the second trigger will be held pending and a trigger
overrun error will occur. The error condition may be cleared by issuing the Error Query command (E?) and
then reading the response from the DAC488. After the first trigger is processed, the pending trigger will
then be processed. Any additional triggers which may occur while a trigger is held pending will be ignored.