Null Characters Removal For Send Data Using Bidirectional Protocol - Mitsubishi Electric MELSEC iQ-R Series User Manual

25.5
NULL Characters Removal for Send Data using
Bidirectional Protocol
This section explains automatic removal of NULL characters to data to be transmitted using the bidirectional protocol.
Target range of automatic removal of NULL characters
The send data range to which automatic removal of NULL characters is performed is as shown below. However, the automatic
removal of NULL characters is not performed when a response message is transmitted.
Target range of NULL characters automatic deletion
E
Message for data N
Q Data length
transmission
*NULL characters automatic deletion is disabled when transmitting a response message.
When data is transmitted, C24 performs the processing as follows:
• Range of automatic removal of NULL characters
C24 performs the automatic removal of NULL characters to an arbitrary data portion of a message (data length is not
included).
• Automatic removal of NULL characters in data portion
C24 deletes NULL characters included in send data, and then transmits data.
• Handling of sum check code
The results of adding the data portion after automatic removal of NULL characters as binary code data are added to the
transmission message as sum check code.
(When byte units are used) Message
E
Data
Data portion
N
length
Q
(0003)
L H
1 2 3 A
05 06 00 31 32 33 41
H H H H H H
Data length after NULL characters
automatic deletion is added.
*1 Calculation of sum check code is shown below:
06H+00H+31H+32H+33H+41H+42H+43H=0162H
Precautions
When the automatic removal of NULL characters is performed to data transmitted using the bidirectional protocol, always
specify the "Word/byte units designation" to "Byte units".
(Arbitrary data)
Sum check
Data portion
Sum check code is calculated
from the data portion/data
length after NULL characters
automatic deletion, and added.
(*1)
Sum
check
code
L H
B C
42 43 62 01
H H H H H
(H) (L)
25 AUTOMATIC REMOVAL OF NULL CHARACTERS INCLUDED IN SEND DATA

25.5 NULL Characters Removal for Send Data using Bidirectional Protocol

code
Buffer memory (transmission area)
(H)
(0008 )
H
00
H
(3231 )
H
32
H
NULL
(0033 )
characters H
00
H
automatic
(4241 )
H
deletion
42
H
(0043 )
H
00
H
(The data count is in word units)
(L)
Transmission
08
H
data count
31
H
33
H
Transmission
data
41
H
43
H
25
415