CIO-DDA06/16 Measurement Computing Analog Output Board

The Measurement Computing CIO-DDA06/16 Analog Output Board has six channels of 16-bit analog output and 24 lines of digital I/O. The analog outputs are from AD660 DACs, with each output buffered by an OP27. Digital I/O is performed with one 82C55 chip.

Analog output ranges are switch-selectable for a Bipolar or Unipolar range. Bipolar ranges are ±10 V and ±5 V. Unipolar ranges are 0 to 10 V and 0 to 5 V.

The analog outputs are jumper-selectable for either individual or simultaneous transfer. When a DAC pair is set for simultaneous update, writing new digital values to the DAC's control register does not update the DAC's voltage output. In this way, the CIO-DDA06/16 may be set to hold new values until all channels are loaded, then update all six channels simultaneously. This is a very useful feature for multi-axis motor control.

The CIO-DDA06/16 digital I/O lines are a direct interface to an 82C55. The 82C55 is a CMOS chip with TTL level inputs and outputs. The 8255 can source or sink about 2.5 mA. This is adequate to switch other TTL or similar inputs, but is inadequate to drive relays, LEDs or solid state relays. The digital I/O is controlled by programming the 8255's mode register. There are three possible modes. The simplest and most commonly used mode is mode 0 - simple input and output.