Miteq D-9301, Operation And Maintenance Manual, Page: 24 / 86

3-5
3.3.2 REMOTE OPERATION
When remote control is installed, the front panel "REMOTE" switch
selects either Local (front panel) or Remote mode of operation
(see Section 3.3.1).
3.3.2.1 RS422/485 Protocol
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.
Data transmission format is a 10 bit sequence consisting of 1
start, 7 data, 1 parity and 1 stop bit. Odd or Even parity is
set from the rear panel "ADDRESS" DIP switch. All characters,
including the checksum character, are checked for parity. If any
character in the message has a parity, framing or overrun error,
the entire message is ignored and no response is made by the
converter.
All messages addressed to the converter are normally acknowledged
with a response message. Before sending the response message a
converter configured for RS422A will check for no activity on the
communication bus for a period of at least one character time.
If the bus is active, the response message will be cancelled.
This allows a controller to rapidly update a number of devices on
the communication bus without having to wait for a response.
When using this method (available only for RS422A) the following
restrictions apply:
- Minimum frequency update period is 100 msecs.
- Multiple commands may not be sent without waiting for
a response from each command.
The converter continually monitors the communication bus and will
accept all commands addressed to it even when in Local mode.
When in Local mode, receipt of any commands other than Status All
or Status Faults will be ignored and the converter will respond
with an error code.