IDEC FC6A-C16K1CE Communications Manual page 91

Note: If you execute two or more RXD instructions with multi-byte start delimiters simultaneously, the start delimiters of those RXD instructions
must be unique from the others. When the length of the multi-byte start delimiters of the RXD instructions is different, the length of the shortest
one is applied to check the duplicated start delimiters. The start delimiter of any of two RXD instructions in the following RXD instructions are
considered the same.
RXD S1
1 16
Const
Receive Format S1
(01h)
Start
Delimiter
RXD S1
1 16
Const
Receive Format S1
(01h)
Start Delimiter
RXD S1
1 16
Const
Receive Format S1
(01h)
Example: Using Multi-byte Start Delimiter
The following example shows the advantages of using a multi-byte start delimiter rather than a single-byte start delimiter. A RXD
instruction processes incoming data from the master station. The incoming data is sent to multiple slave stations 0 through 9, and
the local slave station number is 1. Therefore, incoming data from the master station must be received only when the incoming
data is sent for the slave station 1.
Incoming data
•
Incoming data consists of start delimiter STX, a slave station number which can be 0 through 9, data 0000 through 9999, and end
delimiter CR.
STX
(02h) (3xh) (3xh) (3xh) (3xh) (3xh)
1st
Data: 0000 through 9999
character
Slave Station Number: 0 through 9
Single-byte start delimiter
•
Only the first byte can be the start delimiter. The second byte of the incoming data, which is the slave station number, has to be
stored to data register D0, and extra ladder programming is needed to see whether the slave station number of the incoming
communication is 1 or not. Only when the slave station number is 1, received data stored in D1 is valid for the local PLC.
STX
(02h) (3xh) (3xh) (3xh) (3xh) (3xh)
Start
Delimiter
Stored to D0
FC6A S
D1 D2
M20 D400
DR
D1 D2
M21 D402
Const Skip
(02h)
D1 D2
M22 D404
Const Const Const Const
(02h) (03h) (04h) (05h)
Start Delimiter
CR
(13h)
Last character
CR
(13h)
Stored to D1
End
Delimiter
M S A -
ERIES ICRO MART LL
5: U
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IN NE YPE OMMUNICATION
C
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M FC9Y-B1730
ANUAL
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