Buffer Memory Read And Write; Commands And Buffer Memory - Mitsubishi Electric MELSEC-A AlSJ71C24-R2 User Manual

8. COMMUNICATIONS USING DEDICATED PROTOCOLS
MELSEC-A
8.9
Buffer Memory Read and Write
This function is used to read from and write to the A1 SJ71 C24 buffer memory.
When this function is used, communications between the computer and
AlSJ71C24 commences immediately when the computer sends a read or
write request, without waiting for the PC CPU END processing. Therefore,
the time T I , described in Section 8.5, is always equal to zero. The PC CPU
carries out buffer memory read and write using TO and FROM instructions.
The method for specifying the control protocol, meanings, and examples for
carrying out this function are shown below.
8.9.1
Commands and buffer memory
(1) ACPU common commands
Note
: o
.........
Executable
(2) Buffer memory
Buffer memory addresses are O H to 7FFH see (see Section 3.5).
One address consists of 1 word (16 bits).
Read and write are both executed i n word units, regardless of the
wordlbyte unit setting.
POINTI
Buffer addresses 100H to 11FH comprise the special applications area.
The AlSJ71C24 will not operate correctly if any operations other than
those described in the following sections are executed.