119CHAPTER 5 CPU ARCHITECTURE5.4.4 Short direct addressing[Function]The memory to be manipulated in the fixed space is directly addressed with 8-bit data in an instruction word.The fixed space to which this address is applied is a 256-byte space of addresses FE20H through FF1FH. Aninternal RAM and a special-function register (SFR) are mapped at FE20H to FEFFH and FF00H to FF1FH,respectively.The SFR area (FF00H through FF1FH) to which short direct addressing is applied is a part of the entire SFRarea. To this area, ports frequently accessed by the program, and the compare registers and capture registersof timer/event counters are mapped. These SFRs can be manipulated with a short byte length and a few clocks.When 8-bit immediate data is at 20H to FFH, bit 8 of an effective address is set to 0. When it is at 00H to 1FH,bit 8 is set to 1. Refer to [Illustration] on next page.[Operand format]Identifier Descriptionsaddr Label of FE20H to FF1FH immediate datasaddrp Label of FE20H to FF1FH immediate data (even address only)
