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SECTION 2
RS-232 COMMUNICATIONS
NOTE: Minimum requirements to run RS-232 software is
a PC computer with Windows 95.
2.1 Description
Up to ten controllers can be connected in parallel to a single
RS-232 communications port on a PC. Each controller is assigned a
serial number from 0 to 9 known as the RS-232 ID code. The com-
puter uses these numbers to determine which controller unit to address
at a given time. Each controller must have a different ID.
A simple set of menus is provided in the software which allows the
operator to change the settings of each connected controller unit and
display individual operating parameters.
For users with advanced software capabilities, see Section 2.4 for an
operating protocol.
2.2 RS-232 Cable Connections
C
IN
OUT
CONTROLLER
PLUG
C
IN
OUT
CONTROLLER
PLUG
7
9 PIN
COMPORT
5
3 WIRE CABLE
3
2
25 PIN
COMPORT
7
3 WIRE CABLE
2
3
2.3 Operating Protocol for RS-232 Communications
The CN616 Controller is designed with standard RS-232 three wire serial
communication capabilities. Up to ten controllers can be parallel con-
nected to a single PC. The transmission line is held in tristate to avoid
cross-talk between controllers except when the computer addresses a
specific controller for communication.
Configuration
BAUD rate = 4800
Data bits = 8
Parity = N
Stop = 1
Communication software for the PC is written in Visual Basic. This
software package has been created to operate on PC Windows 95
platform meeting the minimum requirements.
Customers can communicate with CN616 controllers through a PC by
using the following protocol:
• Controllers will not initiate communication. The RS-232
Command Module (computer or similar device) must initiate.
• All communication is in ASCII format
• To start communication, the Command Module must send alert
code ASCII [L] hex 4C. This commands the controllers to cease RS-
232 communication and listen for an RS-232 ID Code. The Command
Module then sends the Identification Number for the controller that it
needs to address, ASCII [0 to 9] hex 30 to 39. The identified controller
will then expect a command code. All the other controllers on-line will
wait for the next alert code.
• Command codes are divided into two groups:
Group 1.
Commands " CAPITAL" requesting data from the
controller.
Group 2.
Commands " small" sending data to the controller.
8
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