Chapter 2 Devices 2.2.13 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 also can 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:
If 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 if 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. 2.2.14 Special Data Registers Every special data register has its definition and specific function.
The system statuses and the error messages are stored in the special data registers. Besides, the special data registers can be used to monitor the system statuses. The special data registers and their functions are listed as follows. As to the SR numbers marked “*”, users can refer to the additional remarks on special auxiliary relays/special data registers. The “R” in the attribute column indicates that the special data register can read the data, whereas the “R/W” in the attribute column indicates that it can read and write the data. In addition, the mark “–” indicates that the status of the special data register does not make any change.
The mark “#” indicates that the system will be set according to the status of the PLC, and users can read the setting value and refer to the related manual for more information. 2-49