Operation | 19
REMOTE OPERATIONS
The equipment is supplied with an RS485/RS422 bus. As an option, the equipment can be supplied with an IEEE-
488, RS232 or contact closure interface instead of the RS485/RS422. The command structures for the serial buses
are identical. The IEEE-488 format is similar, with the exception that no header, address, trailer or checksum bytes are
included in the structure.
SERIAL REMOTE PROTOCOL (RS485/RS422/RS232)
The command structure for the serial buses are identical. All transmissions are multi-byte sequences beginning with a
header byte and ending with a trailer byte. The transmitted byes are all ASCII printable characters in the range of 20H to
7EH.
Serial data format is a 10-bit sequence consisting of 1 Start, 7 Data, 1 Parity and 1 Stop bit. If No Parity is used, then the
data sequence consists of 1 Start, 8 Data, 0 Parity and 1 Stop bit.. If any character in a command message contains an
error (parity, framing or overrun) or the checksum is incorrect, the command is ignored and no response is made. The
remote parameters (Address, Baud, Rate and Parity) are programmable from the front panel. The response time from
command to acknowledge is 100 ms. maximum.
All messages addressed to the equipment are acknowledged with a response message. The unit continually monitors the
communication bus and will accept commands addressed to it, even in Local mode. When in Local mode, receipt of any
SET commands will be ignored and the unit will respond with and error code.
The response time from command to acknowledge is 100 ms. maximum. Since all bytes are ASCII printable characters, a
compatible terminal may be used to control the equipment or monitor traffic on the communication bus.
SERIAL MESSAGE FORMAT
The serial message format is as follows:
HEADER - ADDRESS - COMMAND/ERROR CODE - PARAMETERS - TRAILER - CHECKSUM
The Header byte is 7BH, ASCII character “{“.
The address may take on the values from 64 to 95 decimal (40H to 5FH).
Legacy Redundant Amplifier commands are fully supported in this unit. The new command set is a three ASCII character
indentifier preceded by and ASCII “?” or “$”. Commands preceded by “?” are QUERY commands and those preceded by
“$” are SET commands. Query commands are used to examine system parameters while SET commands are intended to
modify system parameters.
Most set commands, and some query commands, require additional parameters. Parameters are all ASCII printable
characters in the range of 20H to 7EH. Numeric parameters are sent MSD first, LSD last. Values which do not adhere to
the command format, or are beyond the allowable range, will be rejected and cause the unit to respond with an error code.
The Trailer byte is 7DH, ASCII character “}”.
The checksum byte is the sum modulo 95 of all message characters beginning with the header byte up to and including
the trailer byte. The value 32 is subtracted from each character value before taking the modulo 95 sum. The value 32 is
added to the final sum to obtain the checksum value. All values are in decimal.
Checksum = MOD [(character value - 32), 95] + 32
