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SECTION 4
REMOTE OPERATIONS
The equipment is supplied with an RS485/RS422 bus interface and an Ethernet
interface. As an option the unit can be supplied with RS232 instead of the
RS485/RS422 interface.
4.1 SERIAL REMOTE PROTOCOL (RS485/RS422/RS232)
The command structures for the serial buses; RS485, RS422 and RS232 are identical.
All transmissions are multi-byte sequences beginning with a header byte and ending
with a trailer byte and checksum byte. The transmitted bytes are all ASCII printable
characters in the range of 20H to 7EH.
Serial data format is a 10-bit sequence. With parity set to odd or even the data includes
1 Start bit, 7 Data bits, 1 Parity bit, and 1 Stop bit. With the parity set for none the data
includes 1 Start bit, 8 Data bits and 1 Stop bit. All characters, including the checksum
character, are checked for parity. 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 (commands beginning with “$”) will be ignored and the unit will respond with
an error code.
The response time from command to acknowledge is 100 ms. maximum. Since all bytes
are ASCII printable characters, a compatible terminal may be used to control the
equipment or monitor traffic on the communication bus. The serial message format
described below including checksum generation must be adhered to.
4.1.1 SERIAL MESSAGE FORMAT
The serial message format is as follows:
HEADER - ADDRESS - COMMAND/ERROR CODE - PARAMETERS -
TRAILER - CHECKSUM
The Header byte is 123 decimal (7BH, ASCII character "{").
The address may take on the values from 64 to 95 decimal (40H to 5FH, ASCII
characters “@” to “_”).
Commands are three ASCII characters preceded by an ASCII “?” or “$.” 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.