AH500 Programming Manual 4.3 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. The index register is used as follows. 1. Using the register name to modify the device When M0 is ON, E0=10, D0@E0=D (0+10)=D10, and D1=D10. When M0 is ON, E0=10, E1=17, D1@E0=D (1+10)=D11, and the bit part 1@E1=(1+17)=18. However, the maximum bit number is 15. Since m=18/16=1 and n=18%16=2 (getting the remainder), the last modification result is D (11+m).n=D12.2. D12.2 is ON. 4-6