ICS PCI-WDT 500, Руководство по эксплуатации продукта

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Manual Number: 00650-144-1 Page 29
Programming
On the PCI-WDT50x card, the 8254 counters occupy the following addresses:
Base Address Read/Write Counter 0
Base A1 Read/Write Counter 1
Base A2 Read/Write Counter 2
Base A3 Read/Write Counter Control Register
The counters are programmed by writing a control byte into the counter control register. The control
byte specifies the counter to be programmed, the counter mode, the type of read/write operation,
and the modulus. The control byte format is a follows:
7 B 6 B 5 B 4 B 3 B 2 B 1 B 0 B
1 C S 0 C S 1 W R 0 W R 2 M 1 M 0 M D C B
SC0 and SC1: These bits select the counter that the control byte is destined for.
1 C S 0 C S n o i t c n u F
0 0 0 r e t n u o C m a r g o r P
0 1 1 r e t n u o C m a r g o r P
1 0 2 r e t n u o C m a r g o r P
1 1 d n a m m o C e t i r W / d a e R
RW0 and RW1: These bits select the read/write mode of the selected counter.
1 W R 0 W R n o i t c n u F e t i r W / d a e R r e t n u o C
0 0 d n a m m o C h c t a L r e t n u o C
0 1 e t y B S L e t i r W / d a e R
1 0 e t y B S M e t i r W / d a e R
1 1 e t y B S M n e h t , e t y B S L e t i r W / d a e R
M0, M1, and M2: These bits set the operational mode of the selected counter.
e d o M 2 M 1 M 0 M
0 0 0 0
1 0 0 1
2 x 1 0
3 x 1 1
4 1 0 0
5 1 0 1
BCD: Set the selected counter to count in binary (0) or BCD (1).