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1.7.1 Memory area Variables V
The memory area “Variables V” is the retaining memory which is used by
the program to store data of operations. It is composed by 200 locations,
type word (therefore 100 double words). This area may be entered by
operations on bit, word or double word. Number of double word still refers
to the words structure, therefore to enter consecutive variables in double
word the number must be put forward of 2 units. Values are reset at
starting or at reset of PLC.
1.7.2 Area memoria special marker SM
This area is the retaining memory which contains all data used by the
ladder program to interact with the hardware resources of EPL101. Some
of these data are initialized at starting of PLC with default values described
in the table below. This area contains all data related to analog inputs and
also some bits controlled by the PLC for the ladder application as well as
the settings for serial ports. The table below includes the content of each
single location of the are “Special markers”, giving the address for Modbus
protocol and the type of operation allowed for each location (R=reading,
W=writing, R/W=reading/writing).
SM n°
Mod.
word
Description/Meaning
SM0
2
000
Status bit
Bit 0
RUN/STOP bit (1=run). At starting this bit is
always forced to ON, obtaining the RUN mode
of PLC. In STOP mode, the relay outputs of
PLC are disabled.
R/W
Bit 1 This bit is always ON for first scanning cycle
of main program. Ex. It is used to execute
initialization sub-program.
R
Bit 2 This bit makes available a clock impulse of 60
seconds (ON for 30 seconds, OFF for 30
R
Summary of Contents for EPL101
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