HP (Hewlett-Packard) PCI-9111DG/HR Manual De Usuario

34 

•

 Operation Theorem 

4.5 

Digital Input and Output 

To program digital I/O operation is fairly straightforward. The digital input 
operation is just to read data from the corresponding registers, and the 
digital output operation is to write data to the corresponding registers. The 
digital I/O registers‘ format is shown in section 3.14. Note that the DIO 
data channel can only be read or written in form of 16 bits together. It is 
impossible to access individual bit channel. 

The PCI-9111 provides 16 digital input and 16 digital output channels 
through the connector CN1 and CN2 on board. The digital I/O signal is 
fully TTL/DTL compatible. The detailed digital I/O signal specification can 
be referred to section 1.3. 

 

Digital Output (DO) 

Digital GND (DGND) 

Digital Input(DI) 

From TTL Signal

 

To TTL Devices

 

PCI-9111

 

Outside Device

 

74LS244  

74LS373  

 

4.6 

Timer/Counter Operation 

One 8254 programmable interval timer/counter chip is installed on 
PCI-9111. There are three counters in one 8254 chip and 6 possible 
operation modes for each counter. The block diagram of the timer/counter 
system is shown in following diagram. 

 

Counter #0

 

Internal 2 MHz Clock   

Timer #1

 

Internal Timer Pacer 

Timer #2

 

8254 Chip 

  G 
  C 

  G 
  C 

  G 

  O 

  O 

  O 

'H' 

'H' 

AD Trigger Signal 

Gate Control 

Pre-Trigger 

Control 

Pre-Trigger 

Signal 

  C