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3 SPECIFICATIONS
3.5.4 Expansion register (ED0 to ED1023)
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The expansion register is internal memory where 1-word (16-bit) data can be stored.
If the expansion register is used, data can be stored internally in the QD51 (-R24) and
1-word data can be sent and received between tasks and between the QD51 (-R24)
and the programmable controller CPU.
TO
(Writing of data)
Programmable
controller
CPU
FROM
(Reading of data)
REMARK
1 The data in the expansion register are not backed up by a battery, so if the
programmable controller's power is turned OFF or it is reset, the data written to
the register are erased.
If the data need to be held even after the programmable controller is powered
OFF or reset, save the expansion register data in the following devices.
• File register of the programmable controller CPU
• Latched device of the programmable controller CPU
2 When data are sent and received between devices in 1-word units, the buffer
memory (Refer to Section 3.5.2) and common memory (Refer to Section 3.5.3)
can also be used.
(1) Writing data to and reading data from the expansion register
Data are written to or read from the expansion register by the following methods.
• Using the special variable W@ of the BASIC program
• Using the GETMEM/PUTMEM command in the BASIC program
• Using the FROM/TO command in the sequence program
The method of designating the expansion register differs in the special variable
W@, the GETMEM/PUTMEM command and the FROM/TO command, as shown
below.
2
QD51(-R24)
W@/GETMEM
(Reading of data)
Expansion
Register
W@/PUTMEM
(Writing of data)
MELSEC-Q
1
BASIC
program
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