126
CHAPTER 5 CPU ARCHITECTURE
5.4.5 Short direct addressing
[Function]
This addressing directly addresses a memory area to be manipulated from a fixed space by using the 8-bit data
in an instruction word.
This addressing is applicable to the fixed 256-byte space of FE20H-FF1FH. The internal high-speed RAM is
mapped to addresses FE20H-FEFFH, and special function registers (SFRs) are mapped to addresses FF00H-
FF1FH.
The SFR area (FF00H-FF1FH) to which short direct addressing is applied is one part of all the SFR areas. In
this area, ports, compare and capture registers of timer/event counters that are frequently accessed on program
are mapped. These SFRs can be manipulated with a few bytes and clocks.
Bit 8 of the effective address is 0 if the 8-bit immediate data is in a range of 20H-FFH, and 1 if the data is in a
range of 00H-1FH. Refer to
[Operation]
on the next page.
[Operand Format]
Representation
Description
saddr
Label or immediate data FE20H-FF1FH
saddrp
Label or immediate data FE20H-FF1FH (even address only)