Introducing The Pcim-Dda06/16; Functional Block Diagram - Measurement Computing PCIM-DDA06/16 User Manual

Introducing the PCIM-DDA06/16

The PCIM-DDA06/16 has six channels of analog output and 24 bits of digital input/output. Analog outputs are
from AD660 DACs, with each output buffered by an OP27. Digital I/O is performed with an 82C55.
Analog output ranges are either Bipolar or Unipolar. Bipolar ranges are ±10 V and ±5 V. Unipolar ranges are 0
to 10 V and 0 to 5 V. You set the analog output range for each DAC with an onboard switch. You set the analog
outputs for simultaneous or individual transfer with an on-board jumper.
The PCIM-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 enough to switch other TTL or
similar inputs, but is inadequate to drive relays, LEDs or solid-state relays without additional buffering.
The 82C55 digital I/O chip initializes all ports as inputs on power-up and reset.
The PCIM-DDA06/16 digital I/O is controlled by programming the 8255's mode register. There are three
possible modes. The most commonly used mode is Mode 0, simple input and output.

Functional block diagram

The PCIM-DDA06/16 board consists of two functional sections: analog output and digital I/O. The digital I/O
section consists of a single 82C55, and a 24-line digital I/O chip. The analog output section consists of six
identical circuits, each consisting of a DAC, an OP27 output buffer, and a gain range control switch. You can
control each analog output individually or control all six outputs simultaneously.
PCIM-DDA06/16 functions are illustrated in the block diagram shown here.
Figure 1. Functional block diagram
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Chapter 1