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Page: 86 Model MRC88m / MRAUDIO8x8m
© 2009 Xantech Corporation
Section 9: Appendix
RS232 CONTROL
This document describes the bi-directional RS232 interface of the MRC88m using the COM PORT on the rear
of the system (Fig. 3-29). This interface allows an external RS232 device to control the MRC88m via a set of
ASCII text commands. It is also possible to control any IR device connected to the MRC88m system as well by
triggering individual IR Commands and/or IR Macros via ASCII strings.
In EXPANDED Mode, the Primary and Secondary units RS232 ports are both active although only the
Primary’s RS232 port will be bi-directional. The Secondary units RS232 port can only be used as a Control
INPUT.
EXAMPLE: Interface the Primary’s RS232 port to a Lighting/HVAC/Security system allowing the MRC88m
system to control the other system or be controlled by it (bi-directional control). The Secondary units RS232
port can be connected to a touch screen controller for a Master Controller for the entire system including control
of the Lighting/HVAC/Security system connected to the Primary units RS232 port.
TYPES OF COMMANDS
There are two types of information that can be sent to the MRC88m Controller: COMMANDS and QUERIES.
COMMANDS are ASCII strings used to set a specific parameter in the system (i.e. Select a Source, turn a zone
ON, start a DVD player etc…). QUERIES are requests for system status information and result in the MRC88m
controller sending back a reply to the string being sent (i.e. seeing what zones are on, which sources are
selected and volume settings etc….)
INTERFACING TO THE RS232 COMPORT
The RS232 Com Port on the rear of the MRC88m Controller, is wired as a ‘null modem’ end, meaning the
Transmit and Receive line have already been interchanged for direct communication with a PC. What this
means is when connecting to a standard PC’s Com Port, no Null Modem cable is necessary.
The pin out configuration for this connector is:
COM PORT
PIN # FUNCTION
1, 7, 8, & 9 NC
2 Tx
3 Rx
4 DSR
5 GND
6 DTR
Table 2: Rear Com Port Connector Pin Out
ASCII STRING ‘INITIATING’ AND ‘TERMINATING’ CHARACTERS
The protocol was designed to be similar to the one used in the Xantech ZPR68 so that it would be familiar. It is
different from the ZPR68 in that the MRC88m has a buffered UART and is therefore able to receive a complete
command/query string at one time.