Chapter 2 Devices 2.2.13 Data Registers (D) The data register stores 16-bit data. The highest bit represents either a positive sign or a negative sign, and the values that the data registers can store range between -32,768 to +32,767. Two 16-bit registers can be combined into a 32-bit register; for example, (D+1, D) in which the lower number register represents the low 16 bits. The highest bit represents either a positive sign or a negative sign, and the values that the data registers can store range between -2,147,483,648 to +2,147,483,647.
2_ Four 16-bit registers can be combined into a 64-bit register; for example, (D+3, D+2, D+1, D) in which the lower number register represents the lower 16 bits. The highest bit represents either a positive sign or a negative sign, and the values that the data registers can store range between -9,223,372,036,854,776 to +9,223,372,036,854,775,807. You can also use the data registers to refresh the values in the control registers in the modules other than digital I/O modules. Refer to the ISPSoft User Manual for more information on refreshing the values in the control registers. There are two types of registers. General-purpose registers:
When the PLC changes to RUN, or is disconnected, the value in the register is cleared to zero. If you want to retain the data when the PLC changes to RUN, Refer to the ISPSoft User Manual for more information. Note that the value is still cleared to zero when the PLC is disconnected. Latched register: If the PLC is disconnected, the data in the latched register is not cleared. In other words, the value before the disconnection is retained. If you want to clear the data in the latched area, you can use the RST or ZRST instructions. 2.2.14 Special Data Registers (SR) Every special data register has its own definition and specific function.
System status and the error messages are stored in the special data registers. You can also use special data registers to monitor the system statuses. The special data registers and their functions are listed in the table below. • For SR numbers marked “*”, Refer to the additional remarks in Section 2.2.1.6 on special auxiliary relays/special data registers. • The “R” in the attribute column indicates that the special data register can read the data; “R/W” in the attribute column indicates that it can read and write the data. • The “–” indicates that the status of the special data register does not make any change.
• The “#” indicates that the system is set according to the status of the PLC, and you can read the setting. Refer to the related manual for more information. • The “Y” in the column latched means it is latched, the “N” means it is non-latched; and “H” means it follows the settings in HWCONFIG. 2-67