Access PCI-DIO-24D(H) 用户手册

The counters are programmed by writing a control byte into the counter control register. Refer to the 
previous register map for the base addresses of the counters and 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 as follows: 
 

B7 B6 B5  B4  B3 B2 B1 B0 

SC1 SC0 RW1 RW0 M2

M1

M0

BCD 

  
 

SC0-SC1: These bits select the counter that the control byte is destined for. 

 

 

0 

0 

Program Counter #0 

0 

1 

Program Counter #1 

1 

0 

Program Counter #2 

1 1 

Read/Write 

Cmd.* 

  

* See section on Reading and Loading the Counters. 

  
 
 

RW0-RW1: These bits select the read/write mode of the selected counter. 

 

  RW0

 

0 

0 

Counter Latch Command 

0 

1 

Read/Write LS Byte 

1 

0 

Read/Write MS Byte 

1 

1 

Read/Write LS Byte, then MS Byte 

  
 

M0-M2: These bits set the operational mode of the selected counter.  

 

 

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 (BCD = 0) or BCD (BCD = 1). 

Manual PCI-DIO-24DH 

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