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MELSEC-Q
4 FUNCTIONS
(3) Separation prevention by dedicated instruction
The separation prevention function is executed using the BBLKRD instruction
(read) and BBLKWR (write) which are the dedicated instructions for
reading/writing of the buffer memory from and to QJ71PB92D.
When the writing/reading of the buffer memory are executed using the FROM/TO
instruction, the separation prevention function cannot be used.
(a) For detail of the BBLKRD instruction, refer to section 8.1.
For detail of the BBLKWR instruction, refer to section 8.2.
(b) Use the BBLKRD instruction and BBLKWR instruction in pairs, and ensure
to execute for each sequence scan (Refer to the program example in section
7.4).
Even when either of the reading of input data and writing of output data is
not required, read/write the dummy input data or output data using the
BBLKRD/BBLKWR instructions.
When only either of the BBLKRD instruction and BBLKWR instruction is
used, the transmission delay time becomes longer.
G.BBLKRD U0 K0 D0 K10
G.BBLKWR U0 K960 D0 K10
Program processing input and output data
(c) Before the dedicated instructions (BBLKRD/BBLKWR) are executed, the
dedicated instruction valid signal (Y0C) must be turned ON.
If the dedicated instruction valid signal (Y0C) is turned OFF, the dedicated
instructions (BBLKRD/BBLKWR) will become invalid.
