Chapter 6 Applied Instructions 6.7.2 Explanation of I/O Refreshing Instructions Symbol: D ： I/O point whose state is refreshed Bit n ： Number of I/O points whose states are refreshed 1~256 Explanation: The I/O states are not refreshed until the instruction END is executed. When the scanning of the program starts, the states of the external inputs are read and stored in the memory. After the instruction END is executed, the states of the outputs in the memory is sent to the output terminals. Therefore, users can use this instruction when they need the latest I/O data in the operation process. Example 1: When X0.0 is ON, the PLC reads the states of the inputs X0.0~X0.15 immediately.
The input signals are refreshed without any delay. Example 2: When X0.0 is ON, the output signals from Y0.0~Y0.7 are sent to the output terminals. The output signals are refreshed immediately without the need to wait for the execution of the instruction END. Additional remark: 1. If D + n -1 exceeds the device range, the instruction is not executed, SM0 is ON, and the error code in SR0 is 16#2003. 6-153 API Instruction code Operand Function 0600 REF P D, n Refreshing the I/O Device X Y M S T C HC D L SM SR E PR K 16# “$” DF D n Pulse instruction 16-bit instruction (5 steps) 32-bit instruction AH500 AH500 －