72-channel digital I/O | Model 621

Model 621 72-channel digital I/O
  • 72 bi-directional TTL lines, programmable in banks of 8
  • 64 lines have edge detection and interrupts
  • 8 lines have input strobe and output enable control
  • Output driver readback


Model 621 is a low-cost PCI digital I/O board for interfacing a large number of discrete logic signals to PCI computers. Its 72 I/O lines are software programmable as inputs or outputs in banks of eight lines.

Typical Model 621 Application


Edge detection

When enabled, sixty four of the lines can detect logic state changes. A flag is set in a 64-bit register for each input that changes state. The register may be polled to determine which inputs have changed state. The 621 may optionally generate an interrupt whenever state changes occur.

Synchronous I/O

Eight of the 72 I/O channels have special functionality. When programmed as inputs they may be used to latch input data upon command from an external strobe signal.

If these eight lines are programmed as outputs, an external strobe signal can tri-state/enable the data outputs. For additional flexibility, the data direction of these special I/O lines are programmable in two 4-bit blocks.

External relays

The 621 adapter may be connected to as many as three Model 720RB solid-state relay boards. Each 720RB relay board accepts twenty four industry standard relays.


Number of I/O channels72 bi-directional, TTL
Update rate5 MHz
Programmable I/O blocksEight 8-bit blocks and two 4-bit blocks
Source current per channel12 mA
Sink current per channel12 mA
I/O connector80-pin
Compatible relay boardModel 720RB
Power supply requirements5 V (at 200 mA)
Mating ConnectorRobinson Nugent P50E-080P-1-SR1-TG
Dimensions(W x H): 4.786 x 3.950 inches


File Version Type Size
Model 621 Instruction Manual1.0.3PDF289 KB


File Version Type Size
Linux software development kit1.0.0TAR110 KB
Windows software development kit
for 32-bit Windows XP
1.0.0ZIP38 KB
Windows software development kit
for Windows 7, Windows 10 64-bit
2.0.0ZIP3.93 MB
Other Operating Systems
Need a software development kit for another operating system? We can port our SDK to
your OS or provide the information you need to do it yourself. Contact Sales for details.

Pricing & Ordering

Model Description Qty 1 Qty 2-9 Order Qty.
62172-channel digital I/OCallCall 

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