Analog and Digital I/O

Model 426

Features
Six quadrature encoder channels
 with 24-bit resolution

Four 14-bit D/A outputs

Sixteen 14-bit differential A/D inputs, 50 kHz rate, FIFO buffer

Watchdog timer

Forty-eight bi-directional digital signals for solid state relay boards

32 programmable interrupts for counters and digital I/O

Half-size PC/ISA compatible

Description
The Sensoray Model 426 low cost interface saves space in ISA bus systems by combining five functions into a half-size module. Five flat cables connect the Model 426 to external breakout boards.

Encoders
Six 24-bit up/down counter channels are optimized for incremental encoders. Each channel accepts two phased TTL or RS-422 signals plus an index signal to track encoder direction and displacement. Each input is conditioned and synchronized to the 426’s internal clock. Unlike conventional counters, the 426’s counters do not accumulate errors when the encoder dithers or changes direction. The 426 supplies 5 volt power to each encoder channel. All counters are programmable and may optionally generate interrupts.

A/D
Sixteen differential input channels are multiplexed to a sample/hold and successive approximation A/D. A software-programmable amplifier allows gains of 1,2,4,8 for Model 426A and gains of 1,10, 100, 1000 for model 426B. A 512 sample FIFO is available for storing A/D readings.

D/A
Four voltage outputs may be programmed for +/- 10 volts. A unique circuit prevents unpredictable D/A outputs during CPU initialization. All outputs are reset to zero volts whenever a bus reset occurs.

Watchdog
The 426’s watchdog timer may be connected to the bus reset via a 2-pin connector. It may be enabled or disabled under program control. The timer is automatically disabled whenever a bus reset occurs.

Digital I/O
The model 426’s forty-eight digital lines have standard pin outs for solid-state relay boards. Each line is software programmable as an input or output. Thirty-two inputs may be programmed for edge detection and interrupts. The status of output lines may be monitored by software. Whenever a system reset occurs all output channels are turned off.

2-pin connector may be connected to th bus reset line to allow a system reset from software