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78 T1-16S User’s Manual
6. Programming Information

Counter devices and registers (C./C)

The counter registers (C) are used for storing the count value of the counter (CNT)
and the up-down counter (U/D) instructions.
The counter devices (C.) work as the output of the counter instructions.
It is possible to specify the C registers as retentive to retain their data in the event of a
power failure. See section 5.3.

Data registers (D)

Functionally the data registers (D) are the same as auxiliary relay registers (RW)
except that the D registers cannot be used as devices.
A part of the data registers are saved in the built-in EEPROM as fixed data and
transferred into the RAM at the initial load.
The range of the data registers saved in the EEPROM can be specified by SW55.
See section 5.2.
It is possible to specify the D registers as retentive to retain their data in the event of a
power failure. See section 5.3.

Index registers (I, J, and K)

These index registers are used for indirect addressing for a register.
For example, if the value of I is 100 in the following register expression, it designates
D0100. For details, refer to section 6.2.
I
D0000 D0100 if I=100