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I/O Memory Areas Section 9-2
Counter Area There are two counter data areas, the Counter Completion Flags and the
Counter Present Values (PVs). Up to 4,096 counters with counter numbers
C0000 to C4095 can be used. The same number is used to access a
counter’s Completion Flag and PV.
Counter Completion Flags
These flags are read as bits. A Completion Flag is turned ON by the system
when the corresponding counter counts out (the set value is reached).
Counter PVs
The PVs are read and written as words (16 bits). The PVs count up or down
as the counter operates.
Condition Flags These flags include the Arithmetic Flags such as the Error Flag and Equals
Flag which indicate the results of instruction execution as well as the Always
ON and Always OFF Flags. The Condition Flags are specified with labels
(symbols) rather than addresses.
Clock Pulses The Clock Pulses are turned ON and OFF by the CPU Unit’s internal timer.
These bits are specified with labels (symbols) rather than addresses.
Task Flag Area (TK) Task Flags range from TK00 to TK31 and correspond to cyclic tasks 0 to 31.
A Task Flag will be ON when the corresponding cyclic task is in executable
(RUN) status and OFF when the cyclic task hasn’t been executed (INI) or is in
standby (WAIT) status.
Index Registers (IR) These registers (IR0 to IR15) are used to store PLC memory addresses
(absolute memory addresses in RAM) to indirectly address words in I/O mem-
ory. The Index Registers can be used separately in each task or, for CJ1-H or
CJ1M CPU Units, they can be shared by all tasks.Data Registers (DR)
Data Registers (DR) These registers (DR0 to DR15) are used together with the Index Registers.
When a Data Register is input just before an Index Register, the content of the
Data Register is added to the PLC memory address in the Index Register to
offset that address. The Data Registers are used separately in each task or,
for CJ1-H or CJ1M CPU Units, they can be shared by all tasks.
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