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8. COMMUNICATIONS USING DEDICATED PROTOCOLS
MELSEC-A
8 . 8 . 9 Monitoring the extension file register
Monitor data registration is the function that registers the name and the
number of the device to be monitored by the computer to the AJ71 C24. The
monitor is the function that (a) reads the data content of the device
registered at the time the monitor read command is executed by the com-
puter, and (b) executes the corresponding processing such as monitoring.
The device numbers must be consecutive when the device is read using the
batch read (ER) or direct read (NR) command. However, when this function
is used, it is possible to read and monitor the devices Dy designating the
device numbers at random.
(1) Control procedure for monitoring
Eoiiing EM command and
trans-
m:ning device designat'on
I
I
Read processing
(Executing EM commands)
I
Data processing
Change monitor device?
+
POINT
(1) As the flowchart shows, monitor data registration must be executed
before monitoring. Attempting to execute monitoring without register-
ing the monitor data will cause a protocol error.
r
(2) The contents registered in monitor data registration are cleared when
the power supply is turned OFF or the PC CPU is reset.
(3)
For monitor registration, five types of registration are possible. They
are device memory in bit units (BM or JM), device memory in word units
(WM or QM) and the extension file register (EM).
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