Comtech EF Data CRS-300 - Manual (Page 219)

CRS-300 1:10 Redundancy Switch MN/CRS300.IOM
Serial-based Remote Product Management Revision 19
7–3
• Individual commands responses are faster than those to global commands (MGC). More parameters require more time.
• A pass-through command is passed with little inspection by the switch,but remember the modem being addressed may be at
the distant end of an EDMAC link! Types of pass-through commands:
o To a local modem;
o To a modem at the distant end (EDMAC);
o To a local BUC or transceiver connected to a local modem;
o To a distant end BUC or transceiver through the distant end modem.
7.5 Basic Protocol
Whether in EIA-232 or EIA-485 mode, all data is transmitted as asynchronous serial characters, suitable for transmission and reception
by a Universal Asynchronous Receiver/Transmitter (UART). The asynchronous character format is 8-N-1 (8 data bits, no parity, 1 stop
bit). The baud rate may vary from 1200 to 57600 baud.
All data is transmitted in framed packets. The Controller is in charge of the process of monitor and control, and is the only device that
is permitted to initiate, at will, the transmission of data. Targets are only permitted to transmit when they have been specifically
instructed to do so by the Controller.
All bytes within a packet are printable ASCII characters, less than ASCII code 127. In this context, the Carriage Return and Line Feed
characters are considered printable.
All messages from Controller-to-Target require a response, with one exception: This will be either to return data that has been
requested by the Controller, or to acknowledge reception of an instruction to change the configuration of the Target. The exception to
this is when the Controller broadcasts a message (such as Set Time/Date) using Address 0, when the Target is set to EIA-485 mode.