PXI-6533 PXI/CompactPCI National Instrument

Title: Understanding and Utilizing NI 653x Digital I/O Devices

Introduction: The NI 653x devices stand out as high-speed, 32-bit, parallel, digital I/O interfaces tailored for various computer architectures, including PCI, PXI/CompactPCI, PCMCIA, and ISA. Driven by the specialized National Instruments DAQ-DIO ASIC, these devices are designed to deliver superior performance for plug-in DIO applications. This article explores their capabilities, focusing on unstrobed I/O, pattern I/O, and handshaked I/O, achieving speeds up to 20 MHz, or 80 Mbytes/s for 32-bit transfers (NI 6534).

Hardware Overview:

1. Data Latches and Drivers:
   • The 32 digital I/O lines are organized into four 8-bit ports, allowing flexible configuration.
   • Ports can be grouped into two 8-bit or 16-bit groups for pattern I/O or handshaking, or as a single 32-bit group.
   • Each I/O line is 5 V TTL/CMOS compatible, supporting various configurations.
   • Configurable as inputs or outputs, with options for standard or wired-OR outputs.
   • Wired-OR outputs provide unique capabilities, allowing two or more outputs to drive a single line.
2. Pattern I/O and Handshaking I/O:
   • Pattern I/O enables controlled input or output of patterns synchronized to a clock signal.
   • Handshaking I/O facilitates seamless interfacing with peripheral devices, ensuring data transfer only when both the NI 653x and the peripheral are ready.
   • Detailed information on these features is available on page 330 in the Digital I/O overview and page 732 in the Digital I/O tutorial.
3. Change Detection:
   • The 653x devices can be programmed to acquire data when specified digital input lines undergo a state change.
   • For more details on change detection capabilities, refer to page 330 in the Digital I/O overview and page 732 in the Digital I/O tutorial.

Conclusion: Understanding the capabilities of NI 653x digital I/O devices opens up opportunities for high-speed, deterministic data transfer and pattern-based operations. Whether configuring for unstrobed I/O, pattern I/O, or handshaking I/O, users can leverage the flexibility and performance of these devices to meet their specific application requirements. Additionally, the change detection feature adds versatility, making the NI 653x devices suitable for a wide range of digital I/O applications. For in-depth information, refer to the provided documentation on Digital I/O overview and tutorial pages.