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CHAPTER 3 CPU ARCHITECTURE
Preliminary User’s Manual U13420EJ2V0UM00
3.4.4 Short direct addressing
[Function]
The memory to be manipulated in the fixed space is directly addressed with 8-bit data in an instruction word.
This addressing is applied to the 256-byte space FE20H to FF1FH. An internal RAM and a special-function
register (SFR) are mapped at FE20H to FEFFH and FF00H to FF1FH, respectively.
If the SFR area (FF00H to FF1FH) where short direct addressing is applied, ports which are frequently accessed
in a program and a compare register of the timer/event counter and a capture register of the timer/event counter
are mapped and these SFRs can be manipulated with a small number of bytes and 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 the [Illustration] on the next page.
[Operand format]
Identifier
Description
saddr
Label of FE20H to FF1FH immediate data
saddrp
Label of FE20H to FF1FH immediate data (even address only)
Содержание mPD780065 Series
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