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Chapter 5
the analog output operation. The minimum frequency is 156.2 S/s, the
maximum frequency is 1 MS/s.
External D/A Output Clock
The external D/A output clock is useful when you want to pace analog
output operations at rates not available with the internal D/A output
clock, or when you want to pace at uneven intervals, or when you
want to start pacing on an external trigger event. Connect an external
D/A output clock to screw terminal AO_CLK on the PCLD-8712 screw
terminal board. Conversions will start on the rising edge of the external
D/A output clock signal. You can use software to specify the clock
source as external. Subsequently, the clock frequency that of the
external D/A output clock input signal from the screw terminal board.
The PCI-1712 supports the following trigger sources for continuous
output mode:
Software trigger,
External digital (TTL) trigger
With PCI-1712, user can define the type of trigger source as rising-
edge or falling-edge.
The following section describes these trigger sources in more detail.
Software Trigger
A software trigger event occurs when you start the analog output
operation (the computer issues a write to the board to begin conver-
sions). When you write the value to analog input trigger flag
AO_TRGF on BASE+A to produce either a rising-edge or falling-edge
trigger, depending upon the trigger source type you choose. This edge
will then act as a D/A trigger event. For detailed information, please
refer to Appendix D.7 A/D Control/Status Register.
External Digital (TTL) Trigger
For analog output operations, an external digital trigger event occurs
when the PCI-1712 detects either a rising or falling edge on the External
D/A TTL trigger input signal from screw terminal AO_TRG on the
PCLD-8712 screw terminal board. The trigger signal is TTL-compatible.
PCI-1712/1712L User's Manual
– 42 –
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