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MELSEC-
A
6 EXCHANGING DATA WITH AN EXTERNAL DEVICE
6.4 Exchanging data using the transmission/reception buffer
When using the transmission/reception buffer, data is transmitted and received via the
master station transmission/reception buffer using the FROM/TO command or CC-Link
dedicated commands RIWT(RISEND)/RIRD(RIRCV).
POINT
(1) The address for the transmission/reception buffer differs for the A Series
master module and Q/QnA Series master module.
Refer to section 5.2 for details on changing the banks.
•
A Series master module : Bank 1 M 0H to FFFH
•
Q/QnA Series master module : M 1000H to 1FFFH
(2) When using the RIWT(RISEND)/RIRD(RIRCV) command, the bank is changed
automatically, so it does not need to be changed by the user.
6.4.1 Transmitting data to an external device
The method for transmitting data to an external device using the
transmission/reception buffer is explained in this section.
(1) Flow of process
The flow of the process for transmitting data to an external device using the
transmission buffer is shown below.
R2
RS-232-C
Master station
Bit device
Word device
Remote
input (RX)
Remote
output (RY)
Remote
output (RY)
Remote
input (RX)
Trans-
mission
area
5) Intelligent device
station access
complete ON
7) Intelligent device
station access
complete OFF
2) Intelligent device
station access
request ON
6) Intelligent device
station access
request OFF
Transmission
buffer
Reception
buffer
* When usin
g
the RIWT
(
RISEND
)
command, the steps 2
)
to 7
)
are carried out automaticall
y
.
Programmable controller CPU
External
device
Trans-
mission
9) Data reception
Random data
10) Transmission complete ON
12) Transmission complete OFF
8) Transmission request ON
11) Transmission request OFF
1) Control data +
transmission data
3) Transmission data
4) Control data