5-3
Section
Command and Response Frame Structure
72
BCC Enabled Format (Pin SW3–1 OFF)
Node number
Text
“
jj
”
BCC Disabled Format (Pin SW3–1 ON)
Node number
Text
“
jj
”
Name
Description
STX
This code indicates the beginning of a communications frame. This code is 02h in ASCII.
Node number
This indicates the node number of the Controller that can be set within a range between 00
and 31 (decimal) on the rotary switches of the of the Controller. If a node number is
identically set to one that is set by using the node number setting switch on the Controller, a
response will be returned with the same node number.
ETX
This code specifies the end of the command/response. This code is 03h in ASCII.
BCC
This stands for block check character. The results of horizontal parity calculation from just
after STX through ETX is displayed with a single character. Refer to NO TAG Data Code
Designation for BCC calculation.
The text of a command consists of a command code and an option that specifies
a variety of data items.
After receiving STX, the Controller receives data up to ETX. Then the Controller
will execute the command if the node number in the command is correct. If STX
is received again after the first STX is received and before receiving ETX, the
first STX will be ignored.
Node number Command code
Option
“
jj
”
“
jj
”
Name
Description
Command code
The command code indicates the command that the Controller executes. Refer to 5-3-1
Command List for all command codes available.
Option
Used to designate specified optional settings or to designate read data or write data. For
details, refer to the format of each command.
The text of a response consists of a Retry Flag, command code, response code,
and text data.
Node number
Retry Flag Command code Response code
Text data
“
jj
”
“
jj
”
“
jj
”
“
j
”
Name
Description
Retry Flag
The Retry Flag is set to 0 if ACK OR NACK control is not used.
The Retry Flag is set to 1 and the previous response is returned if no ACK is received within
a specified time in ACK/NACK control.
Command code
The executed command code is sent.
Response code
A response code is attached to the result of command execution and sent to the host. Refer
to 5-12 List of Response Codes.
Text data
Some commands enable the Controller to send data. Refer to the frame structure of each
command for details.
Command
Response
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