Access PCI-DIO-24D(H) Manuel D’Utilisation

  
 

1st Read: 

Status byte 

 

2nd Read: 

Low byte of latched data 

 

3rd Read: 

High byte of latched data 

  
After any latching operation on a counter, the contents of its hold register must be read before any 
subsequent latches of that counter will have any effect. If a status latch command is issued before the 
hold register is read, then the first read will read the status, not the latched value. 
 

 
A simple driver is provided to perform basic counter/timer operations on this card. Source code for the 
driver and a sample program showing how to use the functions are located in the DOS\CSAMPLES 
directory. The following functions are provided: 

 

 
The Frequency Measure function of the 8254 Counter Driver has the ability to measure an unknown 
frequency from 1KHz to 2MHz. This function requires as input the Base Address of the card. The 
unknown frequency is applied to the CLOCK IN pin of the card. The function will return the frequency as a 
long integer in Hz.  
  
 

long frequency_measure(unsigned BaseAddress); 

 

 
The Event Counter function has the ability to trace the number of events that have occurred. This function 
requires the Base Address and an additional parameter that identifies which features should be 
implemented on this call to the function. Each feature can be identified by its unique integer value. 
Multiple features can be run in a single call to the function by ORing the respective integer values 
together. Features will be executed in increasing integer order. The CLOCK IN pin of the card is the point 
of application for the incoming events. (Note: This function is limited by the input speed of the 8254 
counter, and slow signals are preferred. Further only 65,535 events are possible without a RESET.) The 
function returns the number of events (based on priority) or 0 for those features that do not specify a 
return value. 
  
 Features: 
  INITIALIZE 

= 

1; 

initialize 

the 

counter 

  START 

 = 

2; 

begin 

counting 

 

 

SINCESTART  = 4; 

return the number of events since the start 

 

 

SINCELAST 

= 8; 

return the number of events since last check 

  STOP 

 = 

16; 

stop 

counting 

events 

 

 

RESET  

= 32;  reset number of events to 0 

 

 

 

unsigned event_counter(unsigned BaseAddress, int feature); 

 

 
The Generate Frequency function will generate a square wave (0 to +5V) with the desired frequency. The 
Base Address of the card as well as the frequency are required as input to the function. The counter can 
generate a frequency with a range of 1Hz to 250KHz. The square wave can be read on the CLOCK OUT 
pin of the card.  
  
 

void generatefrequency(unsigned BaseAddress, unsigned long frequency); 

  

Manual PCI-DIO-24DH 

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