Mitsubishi MELSEC-A Series Reference Manual page 43

3. TWO-TIER SYSTEM IN THE MELSECNET/B DATA LINK SYSTEM
(2)
Table 3.1 Communicating Stations Available to Peripheral Devices and Special-Function Modules
Master Station
Local Station
Remote I/O Station
Transient transmission function
The transient transmission function (a) reads/writes data from/to a device in a local
station by using a master station programmable controller CPU, and (b)
communicates data between a peripheral device connected to a programmable
controller CPU and a programmable controller CPU in another station.
The transient transmission function executes the following types of processings:
(a) Communications between a master station and a local station
Read/write for devices (T, C, D and W) in a local station by a master station
programmable controller CPU.
*1
LRDP/LWTP instructions in a sequence program are used for this processing
at the master station.
(b) Communications between a master station and a remote I/O station
Read/write of data from/to the buffer memory of a special-function module
connected to a remote I/O station is performed from a master station
programmable controller CPU.
*1
RFRP/RTOP instructions in a sequence program are used at the master
station.
(c) Access between a peripheral device or special-function module and another
station
Another station is accessed from a peripheral device or special-function module
connected to a programmable controller CPU.
As Table 3.1 shows, the accessible station varies depending on the peripheral
device or special-function module installed in a master, local or remote I/O
station.
However, the stations in Table 3.1 are basically accessible.
The manual of the used peripheral device or special-function module gives
details about the functions that can be executed by that peripheral device or
special-function module.
Access target station
*2: Not accessible when using GX Developer
Station where a peripheral device is connected
Master Station Local Station
Accessible
Accessible Not accessible
Accessible Not accessible
*2
3 - 3
Remote I/O Station
Accessible Accessible
Not accessible
Not accessible