Precautions During ProgrammingFP08 − 78.3 Handling Index Registers8.3 Handling Index Registers8.3.1 Index RegistersLike other registers, index registers have two points, IX and IY, for reading and writing16-bit data.Use an index register to indirectly specify a memory area number. (This is also calledindex modification.)Example:Transferring the contents of data register DT100 to the numberspecified by the contents of an index register.R0F0 MV, DT100, IXDT0Base memory area.In this example, the number of the destination data register varies depending on thecontents of IX with DT0 acting as a base. For example, when IX contains K10 thedestination will be DT10, and when IX is K20, the destination will be DT20.In this way, index registers allow the specification of multiple memory areas with a singleinstruction, and thus index registers are very convenient when handling large amountsof data.8.3.2 Memory Areas Which can be Modified with Index RegistersIndex registers can be used to modify other types of memory areas in addition to dataregisters DT.IXWX0, IXWY1, IXWR0, IXSV0, IXEV2, IXDT100Constants can also be modified.IXK10, IXH1001An index register cannot modify another index register.IXIX, IXIYWhen using index modification with an instruction which handles 32-bit data, specifywith IX. In this case, IX and IY are handled together as 32-bit data.Lower 16-bit areaHigher 16-bit areaContents of IXContents of IY