NAiS FP Series, User Manual

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FP
Σ
9.6 Flag Operations When Using Serial Communication
9 - 35
9.6.2 When “STX” is Set for Start Code and “ETX” is Set for End Code
When receiving data:
Relationship between the various flags “Reception done flag and Transmission done
flag” and the F159 (MTRN) instruction
Number of bytes
received is cleared
when F159 (MTRN)
instruction is
executed.
A B
C
STX D
H ETX
<1> <2> <3> <0> <0> <1>
<1>
E ETX
F G
STX
Reception done flag is
turned off by execut-
ing the F159 (MTRN)
instruction.
Reception code is
deleted by F159
(MTRN) instruction.
<1> <2> <2> <0> <1>
Number of bytes
received is
cleared when
start code is
received.
on
off
on
off
External received
data
Reception
done flag
“R9038 or R9048”
F159 (MTRN)
instruction
execution
Reception
buffer
Number of
reception bytes
Stored
* : Write pointer
Cannot be
stored when
reception done
flag is on
Number of bytes
received is
cleared when
start code is
received.
A A A A
B B B B
C
C
C C C
E
E E
E E E E
C C C
C
C
D
D
D D
G G H H
D
Figure 198: FP
Σ
Flag operation when receiving data (STX and ETX setting)
The data is stored in the reception buffer in sequential order, but at the point at which
the start code is received, the number of bytes received is cleared, and the address
(write pointer) is returned to the initial address in the reception buffer.
Reception is disabled while the reception done flag “R9038 or R9048” is on.
When the
F159 (MTRN) instruction is executed, the number of bytes received is
cleared, and the address (write pointer) is returned to the initial address in the reception
buffer.
If there are two start codes, data following the later start code is overwritten and stored
in the reception buffer.
The reception done flag “R9038 or R9049” is turned off by the
F159 (MTRN) instruction.
Because of this, if the F159 (MTRN) instruction is executed at the same time that the
terminal code is received, the reception done flag will not be detected.