NuDAQ PCI-8554, User Manual

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Installation
2.9 Counters Architecture
There are four 8254 chips on PCI-8554 card. The counters on chip
#1 ~ #4 are labeled from counter #1 to counter #12. Counters #11
and #12 are
cascaded counters , and counter #1~ #10 can be
programming to independent or cascaded counters. Table 2.2
illustrates the relationship between the reference number of chips
and the counters number.
8254 Chip
Number
Reference
Number
Counter
Number
Type of
Counter
Counter #1 Independent or Cascaded
Chip #1 U3 Counter #2 Independent or Cascaded
Counter #3 Independent or Cascaded
Counter #4 Independent or Cascaded
Chip #2 U4 Counter #5 Independent or Cascaded
Counter #6 Independent or Cascaded
Counter #7 Independent or Cascaded
Chip #3 U5 Counter #8 Independent or Cascaded
Counter #9 Independent or Cascaded
Counter #10 Independent or Cascaded
Chip #4 U6 Counter #11 Cascaded
Counter #12 Cascaded
Table 2.2 Counters Architecture
There are three signals (2 input,1 output) for each counter, a clock
input signal, a gate control signal, and an output signal. The Figure
2.3 illustrates the block diagram of 8254 counter.
CLK1 ~ CLK12
are clock sources and GATE1 ~ GATE12 are gate control signals.
The COUT1 ~ COUT12 are output of the counters. The Figure 2.4
shows all the labels and the inter-connection of the 8254 counters.
Clock Source Input
Counter / Timer Output
Gate Control Input
Counter
8254 Chip
C
G
O
Figure 2.3 Block Diagram of 8254 Counter