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A H 5 0 0 O p e r a t i o n M a n u a l
5.2.12 Data Registers
The data register stores the 16-bit data. The highest bit represents either a positive sign or a negative sign, and
the values which can be stored in the data registers range from -32,768 to +32,767. Two 16-bit registers can be
combined into a 32-bit register, i.e. (D+1, D) in which the register whose number is smaller represents the low
16 bits. The highest bit represents either a positive sign or a negative sign, and the values which can be stored
in the data registers range from -2,147,483,648 to +2,147,483,647. Besides, four 16-bit registers can be
combined into a 64-bit register, i.e. (D+3, D+2, D+1, D) in which the register whose number is smaller
represents the lower 16 bits. The highest bit represents either a positive sign or a negative sign, and the values
which can be stored in the data registers range from -9,223,372,036,854,776 to +9,223,372,036,854,775,807.
The data registers can also be used to refresh the values in the control registers in the modules other than
digital I/O modules. Please refer to ISPSoft User Manual for more information regarding refreshing the values
in the control registers.
The registers can be classified into two types according to their properties.
1. General-purpose register: When the PLC begins to run, or is disconnected, the value in the register will be
cleared to zero. If users want to retain the data when the PLC begins to RUN, they can refer to ISPSoft
User Manual for more information. Please notice that the value will still be cleared to zero when the PLC is
disconnected.
2. Latched register: If the PLC is disconnected, the data in the latched register will not be cleared. In other
words, the value before the disconnection is still retained. If users want to clear the data in the latched area,
they can use RST or ZRST.
5.2.13 Special Data Registers
Every special data register has its definition and specific function. Please refer to section 2.2.14 in AH500
Programming Manual for more information.
5.2.14 Link Registers
The link register is mainly used in the PLC Link or the Ether Link. When the data exchange occurs between the
AH500 series programmable logic controllers, the link register can be used as the buffer. Please refer to
chapter 11 for more information.
The link registers L0~L65535 add up to 65536 words. (The device range varies with the model selected.)
Besides, the link register can be used as the general auxiliary register.
5.2.15 Index Registers
The index register is the 16-bit data register. It is like the general register in that the data can be read from it and
written into it. However, it is mainly used as the index register. The range of index registers is E0~E13. Please
refer to section 4.2 in AH500 Programming Manual for more information about the usage of index registers.
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