1 configuration of command, Caution – Yokogawa JUXTA VJ Series Limit Alarms User Manual
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<3. PC Link Communication >
IM 77J01J11-01E
3.1.1
Configuration of Command
Commands sent from a higher-level device to VJ Series signal conditioners, consist of the
following elements.
Number of Bytes
1
2
2
1
3
2
1
1
Variable length
(1)
(2)
(3)
(4)
(5)
(7)
(8)
(9)
(6)
Element
STX
Address
number
(ADDRESS)
CPU
number
01
Time to wait
for response
0
Command
Data
corresponding
to command
Checksum
ETX
CR
030102E.EPS
(1)
STX (Start of Text)
This control code indicates the start of a command. The ASCII code is 02 in hexadeci-
mal.
(2)
Address Number (01 to 99)
Address numbers are used by the higher-level device to identify VJ Series signal
conditioners at the communication destination. (They are identification numbers
specific to the VJ Series signal conditioners.)
(3)
CPU number
This number is fixed to “01”.
(4)
Time to Wait for Response
This is fixed to “0”.
(5)
Command (See subsection 3.2.1, “List of Commands”)
Specify a command to be issued from the higher-level device.
(6)
Data Corresponding to Command
Specify an internal register (D register or I relay), number of data pieces, and others.
(7)
Checksum
This converts the ASCII codes of texts between the character next to STX and the
character immediately before the checksum into hexadecimal values and adds them
byte by byte. It then fetches the single lowermost byte of the added results as the
checksum.
This column is required only for PC link communication with checksum. PC link
communication without checksum does not require this 2-byte space of ASCII code.
(8)
ETX (End of Text)
This control code indicates the end of a command string. The ASCII code is “03” in
hexadecimal.
(9)
CR (Carriage Return)
This control code indicates the end of a command. The ASCII code is “0D” in hexa-
decimal.
CAUTION
The control codes “STX”, “ETX”, and “CR” are essential for commands when you create a
communication program for PC link communication. Omission of any of them or incorrect
order of them results in communication failure.
3rd Edition : Oct. 15, 2007-00