User`s manual

Digital Input/Output Boards

Introduction

This section has details on using digital I/O boards in conjunction with the CYDAS UDR Library. Boards

released after the printing of this manual will be described in Readme files on the CYDAS UDR Library disk.

Basic signed integers

When reading or writing ports that are 16-bits wide, be aware of the following issue using signed integers (as

you are forced to do when using Basic):

On some boards, for example the CPDISO 16/P, the

AUXPORT digital ports are set up as one 16-bit port. When

using

cbDOut() or DOut(), the digital values are written as a single 16-bit word. Using signed integers,

writing values above

0111 1111 1111 1111 (32767 decimal) can be confusing. The next increment,

1000 0000 0000 0000, has a decimal value of -32768. Using signed integers, this is the value that you would

use for turning on the MSB only. The value for all bits on is −1. Keep this in mind if you are using Basic,

since Basic does not supply unsigned integers (values from 0 to 65536).

To fully understand and maximize the performance of this and other digital input function calls, refer to the

82C55 data sheet in the Documents subdirectory of the installation. Also refer to the 8536 data sheet (this data

sheet file is not available in PDF format).