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Installation Guide
8254 Counter Timer Pinouts.
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The AD1210, AD1211, AD1220 and AD1221 all have a
16 bit counter timer chip on board. This counter timer greatly
increases the functionality of the A/D cards.
The 8254 has consists of 3 16 bit counters, Counter 0,
Counter 1 and Counter 2. Each counter timer has a clock input,
a gate input and a counter output, these are TTL level signals.
Counter 1 has inputs CLK1, GATE1 and outputs OUT1.
Counter 2 has inputs CLK2, GATE2 and outputs OUT2.
The input to CLK1 is 600kHz from the pacer clock oscillator,
the output OUT1 drives the CLK2 input and the OUT2 output,
under program control, can be used as the A/D converted clock.
When bit 7 of the Timer Xmode register is zero the Pacer clock
output drives the A/D converter. When bit 7 of the Xmode
register is set then the CLK2 output drives the A/D converter.
Counter 0 has inputs CLK0, GATE0 and outputs OUT0. Counter
0 is unused and completely free for the user to program. Its
CLK0 input is shared by the bit 5 Digital Input Port line, pin 34
on the 50 way IDC connector. The GATE0 input is shared by
the bit 6 Digital Input Port line, pin 35 on the 50 way IDC
connector. Since both these lines are inputs they do not effect
the operation of the digital input port.
Counter 0's OUT0 can be output via the bit 7 Digital Input Port
line, pin 36 on the 50 way IDC connector. A jumper on the A/D
card is used to connect OUT0 to Digital Input 7. Since this is an
output driving the line, Digital Input 7 can no longer be used.
__________________________________________ _
Figure 2-15. OUT0 Via Digital Input Bit 7, Pin36.
AD1210/11 and AD1220/21 cards only.
.
OUT0 NOT CONNECTED
OUT0 OUTPUT VIA DIGITAL INPUT 7, IDC PIN36
Chapter 2
AD1200 Reference
DEFAULT
Page 43
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