Dynapro Technologies Dynapro ET TCS, Application Developer'S Manual

Page: 15 / 337

2-1
&+$37(5,17(5)$&,1*727+(+267&20387(5
,1752'8&7,21
This chapter provides information about communication between the Touch Control Screen
(TCS) and host computer. Topics include:
•
A description of serial data
•
Electronics Industries Association (EIA) standards RS-232-E, RS-422-A, and RS-485
•
TCS error checking methods, including buffer overflow control
•
A summary of TCS communication parameters that can be set by the user
•
Multidrop communication protocol
7KH6HULDO,QWHUIDFH
The TCS and the host computer communicate by a serial interface, whereby information is
exchanged between devices as a series of binary codes known as bit-serial data.
%LW6HULDO'DWD
Bit-serial data is digital information represented as a series of bits sent over a wire, one bit at a
time. Specified voltage levels indicate the binary state, either zero or one, of each bit.
7UDQVPLWWHG'DWD
Data bits are sent between the TCS and host in groups of seven or eight bits. Each group of data
bits constitutes one code, and the TCS recognizes 256 such codes from the host. The data bits are
preceded and followed by other bits, described later in this chapter. The number of data bits per
code is controlled by the Data Bits parameter, selectable from the Setup Screen. (Refer to the
ErgoTouch TCS Installation Guide for Setup Screen information.)
TCS operation involves two types of codes: graphic codes and control codes. Graphic codes
generally cause a character to be displayed on the TCS display. Control codes do an action, such
as changing a display characteristic or regulating data flow between the TCS and host.
Chapter 3 explains how TCS handles codes and characters, including the results of using seven
or eight data bits. Appendix C contains detailed information about Standard and Custom
Character Fonts.