DAQ VXI-SC-1102 Manual de instrucciones descargar pdf (Pagina 51)

Chapter 7 PC-TIO-10 Timing I/O Device

DAQ Hardware Overview Guide 7-2 www.ni.com

inputs for counting operations. The Am9513 also makes available five

internal timebases that any counter can use:

• 1 MHz clock (1 µs resolution)

• 100 kHz clock (10 µs resolution)

• 10 kHz clock (100 µs resolution)

• 1 kHz clock (1 ms resolution)

• 100 Hz clock (10 ms resolution)

In addition, you can program the counter to use the output of the next

lower-order counter as a signal source. This arrangement is useful for

cascading-counters. For example, you can program counter 2 to count the

output of counter 1, thus creating a 32-bit counter.

You can configure a counter to count either falling or rising edges of the

selected internal timebase, SOURCE input, GATE input, or the next

lower-order counter signal.

You can use the counter GATE input to gate counting operations. After you

configure a counter through software for an operation, you can use a signal

at the GATE input to start and stop the counter operation. There are eight

gating modes available in the Am9513:

• No Gating—the counter is started and stopped by software.

• High-Level Gating—the counter is active when its gate input is at

high-logic state. The counter is suspended when its gate input is at

low-logic state.

• Low-Level Gating—the counter is active when its gate input is at

low-logic state. The counter is suspended when its gate input is at

high-logic state.

• Rising Edge Gating—the counter starts counting when it receives a

low-to-high edge at its gate input.

• Falling Edge Gating—the counter starts counting when it receives a

high-to-low edge at its gate input.

• High Terminal Count Gating—the counter is active when the next

lower-order counter reaches terminal count (TC) and generates a

TC pulse.

• High-Level Gate N+1 Gating—the counter is active when the gate

input of the next higher-order counter is at high-logic state. Otherwise,

the counter is suspended.

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DAQ VXI-SC-1102 Manual de instrucciones Pagina 51