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Port Configuration and Bidirectional Options for PCMCIA-DIO-24

Hardware: Digital I/O (DIO)>>High-Speed

Problem: Why do the ports of the DIO-24 reset to zero during configuration and reconfiguration? How do I use a port to both read and write without having this happen?

Solution: Any port of the DIO-24 that is an output will go to there initial value of zero whenever a configuration or reconfiguration of any port is executed. This is the expected behavior of the chip used inside of the DIO-24.

If you want to configure all ports as outputs you need to follow the following steps:

1. Configure Port A for output. Configure Port B for output. Configure Port C for output.
   
2. Write pattern to Port A. Write pattern to Port B. Write pattern to Port C.

If you want Port A to be bidirectional (eg. read and write) then the following things must be kept in mind.

1. Port A must be configured as Bi-directional
   
2. There are two handshaking lines that must be used STB (PC4) and ACK (PC6) NOTE: These are both lines on Port C: #4 & #6
   
   
   For "Output" Port A
   
   1. ACK must be held low (0)
      
   2. STB must be held high (1)
      
   3. Write Commands
   
   
   For "Input" Port A
   
   1. ACK must be held high (1).
      
   2. At this point the inputs can be driven, however you have to latch the values by strobing (toggling) STB.
      
   3. Read Commands

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Report Date: 09/09/2004
Last Updated: 09/10/2004
Document ID: 3D8AHBHL

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