PLC in the input and output processing, analog control, position control, the need for many data registers to store data and parameters. The data register is 16 bits and the most significant bit is the sign bit. Two data registers can be used to store 32-bit data, the most significant bit is still the sign bit. The data registers are of the following types:
1. General data register (D0 ~ D199)
A total of 200 points. When M8033 is ON, D0 ~ D199 have power protection function; when M8033 is OFF, they are not power protection, this situation PLC from RUN → STOP or power failure, the data is cleared.
2. Power-down hold data register (D200 ~ D7999)
A total of 7800 points, of which D200 ~ D511 (a total of 12 points) has a power-off function, you can use the external device parameter settings to change the general data register and power-off function data register allocation; D490 ~ D509 for communication; ~ D7999 power off function can not be used to change the software, but the instructions can be used to clear their contents. According to the parameter setting, D1000 or higher can be used as the file register.
3. Special data register (D8000 ~ D8255)
A total of 256 points. The function of the special data register is used to monitor the running status of the PLC. Such as scan time, battery voltage and so on. Unspecified special data registers that the user can not use. For details, refer to the user manual.
4. Index register (V / Z)
FX2N series PLC has V0 ~ V7 and Z0 ~ Z7 a total of 16 index registers, they are 16-bit registers. Index register V / Z is actually a special purpose data register, its role is equivalent to the computer in the index register variable, used to change the component number (index), such as V0 = 5, the implementation of D20V0, The number to be executed is D25 (D20 5). The index register can be read and written like other data registers. When 32-bit operation is required, V and Z can be used in series (Z is low and V is high).

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