Mitsubishi MELSEC-A Series Reference Manual page 31

2. TWO-TIER SYSTEM IN THE MELSECNET DATA LINK SYSTEM
(2) Transient transmission function
The transient transmission function reads/writes data from/to a device in a local
station by the master station programmable controller CPU or communicates data
between a peripheral device connected to a programmable controller CPU and a
programmable controller CPU in another station.
The transient transmission includes the following.
(a) Communication between master station and local station
The device (T, C, D, W) of a local station is read/written from the programmable
controller CPU of the master station.
The master station uses LRDP and LWTP
(b) Communication between master station and remote I/O station
The content of buffer memory of the special function module connected from
remote I/O station is read/written from the programmable controller CPU of the
master station.
The master station uses RFRP and RTOP
(c) Access of peripheral device and special function module to/from other station
Access of the peripheral device and special function module connected to the
programmable controller CPU to/from other station is performed.
The accessible station varies as shown in Table 2.1, depending on which one of
the master station, local station and remote I/O station is connected to peripheral
device or mounts special function module.
For the function executable in the peripheral device and special function module,
refer to the manual for the peripheral device and special function module in use.
Table 2.1 Accessible Stations With a Peripheral Device
Access target station
Master Station
Local Station
Remote I/O Station
*2: Not accessible when using GX Developer
REMARK
1) * 1............. When the AnACPU(P21/R21), AnUCPU or A2US(H)CPU(S1) is
used, the LRDP/LWTP/RFRP/RTOP instructions of the dedicated
instructions can also be used.
(For details of the LRDP/LWTP/RFRP/RTOP instructions, refer to
the AnACPU/AnUCPU Programming Manual (Dedicated
Instructions) IB-66251.)
When the QnACPU, Q2AS(H)CPU(S1) is used, the ZNRD/ZNWR/
RFRP/RTOP instructions of the data link instructions can also be
used.
(For details of the ZNRD/ZNWR/RFRP/RTOP instructions, refer to
the QCPU (Q Mode)/QnACPU Programming Manual (Common
Instructions)SH-080039.)
*1
instructions in a sequence program.
*1
instructions in a sequence program.
Station where peripheral device is connected
Master Station
Accessible
Accessible Not accessible
Accessible Not accessible
*2
2 - 4
Local Station Remote I/O Station
Accessible Accessible
Not accessible
Not accessible