Internal Buffer For Message Reception - Mitsubishi Electric Q12DCCPU-V User Manual

5
ACCESS VIA NETWORK MODULES
5
- 12 5.3 MELSECNET/H Module Access Function
5.3.1 Message communication
(a) Internal buffer for message reception
1) The internal buffer for message reception stores the data received from the
MELSECNET/H module controlled by the C Controller module.
2) The internal receive buffer has the areas for four MELSECNET/H modules,
and up to 128 received data can be stored in each area.
If data are received when the buffer area has been full of received data, they
will be discarded instead of being stored in the buffer.
Therefore, read received data before the number of the data stored in the
internal receive buffer exceeds 128.
3) In message reception, data of the channel specified in the message receiving
function are retrieved from the data stored in the internal buffer.
C Controller module
User program
for message reception
ret = QBF_RECV();
MELSECNET/H module
or
ret = mdReceive();
(For second module)
Figure 5.11 Internal buffer for message reception
Internal buffer
1st
2nd
127th
128th
1st
2nd
127th
128th
(For third module)
1st
2nd
127th
128th
(For fourth module)
1st
2nd
127th
128th
MELSECNET/H module (First module)
Logical channel (Channel 1)
Logical channel (Channel 2)
Logical channel (Channel 3)
Logical channel (Channel 4)
Logical channel (Channel 5)
Logical channel (Channel 6)
Logical channel (Channel 7)
Logical channel (Channel 8)
MELSECNET/H module (Second module)
MELSECNET/H module (Third module)
MELSECNET/H module (Fourth module)