
Model T940 User Manual
Publication No. 980938 Rev. K
Soft Front Panel Operation 5-26
Astronics Test Systems
System Clock
This pull-down control programs the sequencer System Clock source.
The System Clock signal defines the pattern period.
The selections for this pull-down control are:
Table 5-22: System Clock Source Settings
Setting
Description
Typical Usage
Internal
T0CLK
System Clock source set to the
internal period defined by the
sequencer step.
DRM or DRS where internal master clock
timing is acceptable.
AUX1-AUX12 System Clock source set to the
external front panel signal.
Auxiliary line is assigned the function of
external clock where:
AUX1-4: 1kHz-50 MHz (when a
programmable threshold or load is
required with the clock)
AUX5-8: LVTTL source 1kHz-50 MHz
AUX9-12: Single-ended or differential
ECL source from 1 kHz to 50 MHz
ECLTRG0
System Clock source set to the
VXI ECLTRG0.
External clock from another VXI instrument
provided across the VXI backplane.
Pulse
Generator
System Clock source set to the
internal pulse generator signal.
For test purposes or for when pulse width
control of the system clock is required.
Frequency
Synthesizer
System Clock source set the to
the internal frequency
synthesizer signal.
For the purpose of having a self-test.
The relevant VXI
plug&play
API function is:
•
tat964_setSystemClockSource
External Mode
This pull-down control selects the clock edge mode when the System Clock
source is set to any non T0CLK selection.
The selections for this pull-down control are:
Table 5-23: External Mode Settings
Setting
Description
Rising Edge
Use the rising edge of the external signal as the active edge
Falling Edge
Use the falling edge of the external signal as the active edge
Both Edges
Use the rising and falling edge of the external signal as the active edge
Divide by 2
Rising Edge
Divide the external signal by two and use the rising edge as the active
edge
Divide by 2
Falling Edge
Divide the external signal by two and use the falling edge as the active
edge