C-5
Model 0254
Section C Serial Communications Protocol
Installation and Operation Manual
X-SE-0254-eng
Part Number: 541B129AAG
September, 2010
C-3 Serial Command Organization
C-3-1 Command Structures
This protocol was selected to service the need for serial error control while
operating in local or wide area networks to transfer information between a
unit and host computer.
Elements
The command format is a free-form variable entry implementation,
enabling expeditious economic means of achieving required programming
results. Commands are comprised of the following structural elements:
Block Pre-limiter
Sentinel indicating start of multiple packets
message
Packet Pre-limiter
Sentinel indicating start of a packet message.
Information Frame
Contains comma pre-limited fields that start with
the first character immediately following the
message pre-limiter and includes all successive
characters up to and including a comma, which
immediately precedes the first ASCII
hexadecimal checksum character.
Checksum
Two ASCII hexadecimal characters created for a
Model 0254 negated sum of all characters
available in the Information Frame, which is used
by a host computer to check a message packet’s
validity.
Packet delimiter
Sentinel indicating end of a packet message.
Block Delimiter
Sentinel indicating end of multiple packets
message
Transfer
All messages are serial half-duplex send-response types.
Baud Rate = 9600
Mastering
The protocol initiator or originator is the master. The master is responsible
for managing the communication link connection.
