Contemporary Research 232-MCT Manuale del prodotto - Pagina 8

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RS-232 Control Protocol

Overview

The 232-MCT full duplex RS232 scheme enables a system programmer to control all TV Tuner functions as well

as monitor 3 groups of TV Tuner status. All commands are sent as ASCII strings. No delays between characters

or commands are required, as data is interrupt driven and buffered.

The 3 status groups are: Channel/Source Select, Audio Levels/Mode and Front Panel. Each of the groups has

one ASCII status response string containing all of the status data for that group. The current status string of a

group is sent from the 232-MCT whenever a valid command for that group is received by the 232-MCT RS-232

port or front panel. A group's status may be requested at any time via the RS-232 port. Status of all 3 groups is

sent at power up. The format of each group's status response string remains the same always.

Up to 9 232-MCTs may be cabled together and addressed for individual control from a single RS-232 port. Each

232-MCT is assigned a unique unit code (Front Panel Mode 2).

Communications parameters (Front Panel Mode 1) are 300 to 9600 baud, 8 data bits, No parity, and 1 stop bit.

Factory default is 9600 baud, Unit#1.

All settings are saved to NVRAM in the 232-MCT.

General protocol specifications

Characters in command strings to the 232-MCT are common ASCII keyboard characters.

Command strings sent to the 232-MCT begin with the ASCII > (greater than symbol) as an 'Attention' character

and end with carriage return - ASCII CR, Hex $0D, or keyboard Enter - as an 'End-of-command' character.

Responses from the 232-MCT begin with the ASCII < (less than symbol) as an 'Attention' character and end

with a carriage return followed by line feed an ASCII LF or Hex $0A as 'End-of-command' characters. A carriage

return is required at the end of each command and is assumed in all examples

Command String Structure

[Attention] (Unit#) [Command] (Parameters) [Return]

Attention

Single character (>) starts the string

Unit#

The Unit# is expressed as an ASCII 0-9 when used in multiple tuner applications.

To address all units, use a Unit # of 0 (Zero – versions 4.0 and above)

Sending no unit number will default to Unit#1

Command

A two-character command

Parameters

Added attributes to some commands

Return

A carriage return ends the command string, you may use ASCII CR, Hex $0D, or keyboard

'Enter' in programming. For simplicity, the programming examples in the manual will not show

the 'CR' – so remember, you'll need to add it in your control code.

Command and Status Response

Commands can be sent back to back at any time without any delay. To allow for rapid, multiple commands,

status responses are intentionally delayed by about 125mS, sending the most current status in response to

control commands or user actions

Contemporary Research

232-MCT Mono Caption Tuner