IDEC MICROSmart FC6A-C16K1CE, Руководство по связи, Страница: 91 / 252

FC6A S
ERIES
M
ICRO
S
MART
A
LL
-
IN
-O
NE
T
YPE
C
OMMUNICATION
M
ANUAL
FC9Y-B1730 5-15
5: U
SER
C
OMMUNICATION
I
NSTRUCTIONS
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.
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.
•
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.
S1
16
D1
M20
RXD
1
D2
D400
Receive Format S1
Const
(01h)
Start
Delimiter
DR
S1
16
D1
M21
RXD
1
D2
D402
Receive Format S1
Const
(01h)
Start Delimiter
Const
(02h) Skip
S1
16
D1
M22
RXD
1
D2
D404
Receive Format S1
Const
(01h)
Start Delimiter
Const
(02h) DR Const
(03h) Const
(04h) Const
(05h)
STX
(02h) (3xh)
1st
character
(3xh) (3xh) (3xh) (3xh)
CR
(13h)
Data: 0000 through 9999
Slave Station Number: 0 through 9
Last character
STX
(02h) (3xh)
Start
Delimiter
(3xh) (3xh) (3xh) (3xh)
CR
(13h)
Stored to D1
Stored to D0
End
Delimiter