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4.18 Write File Record (FC: 21) (SC: 06)
4
MODBUS(R) STANDARD FUNCTIONS
4.18 Write File Record (FC: 21) (SC: 06)
Writes multiple extension file register values.
(1) Request message format (Master Slave)
* 1 The maximum file number available for the QJ71MB91 slave function is dependant on the file
register size of the mounted programmable controller CPU. ( Section 7.3.2)
(a) Write points of each sub-request
Specify the total points N (n1+...+nm) so that the protocol data unit size of the
response message will not exceed 253 bytes.
*2
2 + m 7 + N 2 253
*2
If the above condition is not satisfied, the request message is discarded.
* 2 When the frame mode is ASCII mode, it is 506 bytes.
Figure 4.94 Write file record (Request message)
Data
(L) (L) (L)
Sub-request 1
. . .
. . .
(L) (L)
Data
(L) (L) (L) (L) (L)
Sub-request m
Function
code
Function
code
(15
H
)
Number of
bytes
m x 7
Reference
number
(06
H
)
Reference
number
(06
H
)
Write head
device number
(0000
H to 270FH)
Write head
device number
(0000
H to 270FH)
Write points
n1
(0001
H to 007AH)
Write points
nm
(0001
H to 007AH)
File number
(0000
H to FFFFH)
*
1
File number
(0000
H to FFFFH)
*1
Device
data
1
Device
data
1
Device
data
n1
Device
data
nm
(Number of bytes m x 7)
(Number of bytes m x 7)
(H) (H)
(H) (H)
(H)
(H)
(H) (H)
(H)
(H)
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