Pre-Read Buffers - Mitsubishi Electric M700V Series Programming Manual

4. Buffer Register

4.2 Pre-read Buffers

Function and purpose
During automatic processing, the contents of 1 block are normally pre-read so that program
analysis processing is conducted smoothly. However, during tool radius compensation, a
maximum of 5 blocks are pre-read for the intersection point calculation including interference
check.
The specifications of the data in 1 block are as follows:
(1) The data of 1 block are stored in this buffer.
(2) Only the significant codes in the significant data section are read into the pre-read buffer.
(3) When codes are sandwiched in the control in and control out, and the optional block skip
function is ON, the data extending from the "/" (slash) code up to the EOB code are not read
into the pre-read buffer.
(4) The pre-read buffer contents are cleared with resetting.
(5) When the single block function is ON during continuous operation, the pre-read buffer stores
the following block data and then stops operation.
Other precautions
(1) Depending on whether the program is executed continuously or by single blocks, the timing of
the valid/invalid for the external control signals for the block skip and others will differ.
(2) If the external control signal such as optional block skip is turned ON/OFF with the M
command, the external control operation will not be effective on the program pre-read with the
buffer register.
(3) According to the M command that operates the external controls, it prohibits pre-reading, and
the recalculation is as follows:
The M command that commands the external controls is distinguished at the PLC, and the
"recalculation request" for PLC -> NC interface table is turned ON.
(When the "recalculation request" is ON, the program that has been pre-read is reprocessed.)
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4.2 Pre-read Buffers