Yokogawa JUXTA VJ Series Limit Alarms - Manual (Page 42)

5-2
<Toc> <Ind> <5. MODBUS Communication >
IM 77J01J11-01E 3rd Edition : Oct. 15, 2007-00
5.1.1 Configuration of Message
Messages sent from the higher-level device to the VJ Series consist of the following ele-
ments.
Number of bytes in RTU mode None
Number of bytes in ASCII mode 2 2
(1) (3) (4) (5) (2) (6)
Element Address
Number
(ADDRESS)
Function Code Start of
Message Mark
Data Error Check End of
Message Mark
None
1 2 2 4n
1 1 2n 2
050103E.EPS
(1) Start of Message Mark
This mark indicates the start of a message. Note that only ASCII mode requires a
colon (:).
(2) Address Number (1 to 99)
Address numbers are used by the higher-level device to identify the VJ Series signal
conditioners at the communication destination. (These numbers are identification
numbers specific to individual VJ Series, which are expressed in a hexadecimal in the
message.)
(3) Function Code (See subsection 5.2.1, “List of Function Codes”)
This element specifies a command (function code) from the higher-level device.
(4) Data
This element specifies D register numbers, the number of D registers, parameter
values, or others in accordance with the function code. (It is expressed in a hexadeci-
mal in the message.)
(5) Error Check
In RTU mode Carried out by the cyclic redundancy check (CRC-16) system.
In ASCII mode Carried out by the longitudinal redundancy check (LRC) system.
(6) End of Message Mark
This mark indicates the end of a message. Note that only ASCII mode requires CR +
LF.