Contemporary Research 17 232-ATSC+ Digital HDTV Tuner
RS-232 Control Protocol
Overview
The 232-ATSC+ full duplex RS-232 enables a system programmer to control all TV Tuner functions as well
as monitor 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. The Power button-
function status from the 232-ATSC+ front panel has been grouped with the Channel/Source for simplicity in
the most common modes of operation. 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-ATSC+
whenever a valid command for that group is received by the 232-ATSC+ 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-ATSC+ units may be cabled together and addressed for individual control from a single RS-232
port. Each 232-ATSC+ is assigned a unique unit code.
Communications parameters (Front Panel Mode 1) are 300 to 19200 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-ATSC.
The tuner will accept non-standard RS-232 control such as voltage that swings from 0 to +5 VDC, commonly
found when IR ports are used to send RS-232 commands.
General protocol specifications
Characters in command strings to the 232-ATSC+ are common ASCII keyboard characters.
Command strings sent to the 232-ATSC+ 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-ATSC+ 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)
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.
(29 pages)
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