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Chapter 5 Programming
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National Instruments Corporation 5-33 AT-MIO-16X User Manual
sequence. All writes are 16-bit operations. All values given are
hexadecimal.
1. Write FF00 + n to the Am9513A Command Register to select the
Counter n Mode Register.
2. Write the mode value to the Am9513A Data Register to store the
Counter n mode value. Am9513A counter mode information can be
found in Appendix C, AMD Am9513A Data Sheet. Use one of the
following mode values:
0225 — Selects 5-MHz clock (from SOURCE2 pin)
0B25 — Selects 1-MHz clock
0C25 — Selects 100-kHz clock
0D25 — Selects 10-kHz clock
0E25 — Selects 1-kHz clock
0F25 — Selects 100-Hz clock
0525 — Selects signal at SOURCE5 input as clock
(counts the rising edge of the signal, 6 MHz maximum)
3. Write (FF08 + n) to the Am9513A Command Register to select the
Counter n Load Register.
4. Write the desired update interval to the Am9513A Data Register to
store the counter n load value.
5. Write the following value to the Am9513A Command Register to
load counter n.
FF41 — Load Counter 1
FF42 — Load Counter 2
FF50 — Load Counter 5
6. Write (FFF0 + n) to the Am9513A Command Register to decrement
Counter n.
7. Write the following value to the Am9513A Command Register to
arm Counter n.
FF21 — Arm Counter 1
FF22 — Arm Counter 2
FF30 — Arm Counter 5
After you complete this programming sequence, Counter n is
configured to generate active-low pulses as soon as the load/arm
counter command is written.