Where can I find information about register level programming the VXI-DIO-128? Hardware: VXI/VME/MXI>>VXI Data Acquisition and Instrument Modules>>VXI-DIO-128
Problem: I will be writing an application using the VXI-DIO-128 that cannot use NI-DAQ and need any information available that will aid me in register level programming. Solution: Understanding the VXI-DIO-128: The VXI-DIO-128 has 128-channels of parallel digital I/O. It uses eight OKI 82C55A PPI (Programmable Peripheral Interface) chips: four control the 64 open-drain output channels, and the other four control the 64 input channels. Each 82C55A PPI has 24 programmable I/O pins that represent three 8-bit ports: A, B, and C. These ports can be programmed as two groups of 12 signals or as three individual 8-bit ports. However, the VXI-DIO-128 uses only ports A and B of each PPI. The lines of ports A and B of the four 82C55A PPI chips that control the output channels are connected to the Texas Instruments TPIC6273DW chip. This gives each digital output line the capability of sinking up to 250 mA at up to 42 V. Also, each output has built-in transient suppression diodes, which protect against the voltage spikes that are generated when relays turn off and on. The VXI-DIO-128 can accept input voltage levels ranging from ±42V, and you can set an input threshold voltage between - 32 and +31.75 V in 250 mV steps. These digital input lines are connected to ports A and B of the four 82C55A PPI chips through a Voltage Divider and Input Buffer (see Figure 4-1. VXI-DIO-128 Block Diagram (Page 4-2) in the VXI-DIO-128 User Manual linked below). Although the 82C55A PPI has three modes of operation, the VXI-DIO-128 uses only one of them, the simple I/O mode (mode 0). The three modes of operation of the 82C55A PPI are: 1) Mode 0: Basic I/O 2) Mode 1: Strobed I/O 3) Mode 2: Bidirectional bus Register Level Programming Considerations: National Instruments does not provide Applications Engineering support for Register-Level Programming, however information is made available for users to perform this themselves. For more information about the 82C55A PPI Register-Level Programming, see the PC-DIO-24 and PC-DIO-96 User Manuals (linked below). These boards also use the 82C55A PPI chip, and they have detailed documentation about Register-Level Programming. However, keep in mind that the PC-DIO-24 and the PC-DIO-96 have additional chips that are not present on the VXI-DIO-128. For more information about the characteristics of the 82C55A PPI, see the Data Sheet either in Appendix C of the PC-DIO-24 or PC-DIO-96 User Manuals or at the OKI Semiconductor web page linked below. Related Links: VXI-DIO-128 User Manual PC-DIO-96 User Manual PC-DIO-24 User Manual OKI Semiconductor - MSM82C55A PPI 2TUACF6W - I am looking for information about special considerations or limitations of the VXI-DIO-128. Where can I find such information? Attachments:
Report Date: 01/30/2003 Last Updated: 02/28/2004 Document ID: 2TT8LH6W |
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