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Chapter 4 Signal Connections
PCI-4451/4452 User Manual 4-20
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National Instruments Corporation
GPCTR0_GATE Signal
Any PFI pin can externally input the GPCTR0_GATE signal, which is
available as an output on the PFI9/GPCTR0_GATE pin.
As an input, the GPCTR0_GATE signal is configured in the edge-detection
mode. You can select any PFI pin as the source for GPCTR0_GATE and
configure the polarity selection for either rising or falling edge. You can use
the gate signal in a variety of different applications to perform actions such
as starting and stopping the counter, generating interrupts, saving the
counter contents, and so on.
As an output, the GPCTR0_GATE signal reflects the actual gate signal
connected to general-purpose counter 0. This is true even if the gate is being
externally generated by another PFI signal. This output is set to tri-state at
startup.
GPCTR0_OUT Signal
This signal is available only as an output on the GPCTR0_OUT pin. The
GPCTR0_OUT signal reflects the terminal count (TC) of general-purpose
counter 0. You have two software-selectable output options—pulse on TC
and toggle output polarity on TC. The output polarity is software selectable
for both options. This output is set to tri-state at startup. Figure 4-10 shows
the timing of the GPCTR0_OUT signal.
Figure 4-10.
GPCTR0_OUT Signal Timing
GPCTR0_UP_DOWN Signal
This signal can be externally input on the DIO6 pin and is not available as
an output on the I/O connector. The general-purpose counter 0 will count
down when this pin is at a logic low and count up when it is at a logic high.
You can disable this input so that software can control the up-down
functionality and leave the DIO6 pin free for general use.
GPCTR0_SOURCE
GPCTR0_OUT
GPCTR0_OUT
(Toggle output on TC)
(Pulse on TC)
TC
User.book Page 20 Tuesday, April 14, 1998 10:20 AM