Analog & Digital Interface

Model 421

Features
Three quadrature encoder channels with 16-bit counters

Four 12-bit D/A outputs

Eight 12-bit differential A/D inputs, 50 kHz rate

Watchdog timer

Forty-eight bidirectional digital signals for solid state relay boards

PC/ISA compatible

Description
The Sensoray Model 421 low cost interface saves space in ISA bus systems by combining five functions into one module. Four flat cables connect the Model 421 to external breakout boards.

Encoders
Three 16-bit up/down counter channels are optimized for incremental encoders. Each channel accepts two phased TTL or RS-422 signals to track encoder direction and displacement. Unlike conventional counters, the 421 counters do not accumulate errors when the encoder dithers or changes direction. The 421 supplies 5-volt power to each encoder channel.

A/D
Eight differential input channels are multiplexed to a sample/hold and successive approximation A/D. A resistor-programmable instrumenta- tion amplifier allows gains of 1 to 1000. The 15-volt outputs from the DC/DC supply ensure A/D linearity for 10 volt input signals

D/A
Four voltage outputs channels may be programmed for 0 to +10 volts. One channel has a remote sense input to minimize line loss errors. All output voltages are reset to zero volts whenever a bus reset occurs.

 Watchdog
The 421's watchdog timer output may be routed to either bus reset or nonmaskable interrupt. It may be enabled or disabled under program control. The timer is automatically disabled whenever a bus reset occurs

Digital I/O
The Model 421 has forty-eight digital I/O lines with industry standard pinouts for solid state relay boards. Each line is software programmable as an input or output. The status of output lines may be monitored by software. Whenever a system reset occurs all output channels are turned off.

Watchdog Timer
Time-out: 500 mS
 2-pin connector may be connected to the bus reset line to allow a system reset from software