UPD78F9500MA-CAC-A Datasheet, PDF (50/342 Pages) Renesas Technology Corp – 8-Bit Single-Chip Microcontrollers

CHAPTER 3 CPU ARCHITECTURE
3.4.2 Short direct addressing
[Function]
The memory to be manipulated in the fixed space is directly addressed with the 8-bit data in an instruction word.
The fixed space where this addressing is applied is the 160-byte space FE80H to FF1FH (FE80H to FEFFH
(internal high-speed RAM) + FF00H to FF1FH (special function registers)).
The SFR area where short direct addressing is applied (FF00H to FF1FH) is a part of the total SFR area. In this
area, ports which are frequently accessed in a program and a compare register of the timer counter are mapped,
and these SFRs can be manipulated with a small number of bytes and clocks.
When 8-bit immediate data is at 80H to FFH, bit 8 of an effective address is cleared to 0. When it is at 00H to
1FH, bit 8 is set to 1. See [Illustration] below.
Identifier
saddr
saddrp
Description
Label or FE80H to FF1FH immediate data
Label or FE80H to FF1FH immediate data (even address only)
[Description example]
EQU DATA1 0FE90H ; DATA1 shows FE90H of a saddr area,
MOV DATA1, #50H ; When setting the immediate data to 50H
Instruction code 1 1 1 1 0 1 0 1 OP code
1 0 0 1 0 0 0 0 90H (saddr-offset)
0 1 0 1 0 0 0 0 50H (immediate data)
[Illustration]
7
0
OP code
saddr-offset
15
8
Effective
address ^{1 1 1 1 1 1 1 α}
When 8-bit immediate data is 20H to FFH, α = 0.
When 8-bit immediate data is 00H to 1FH, α = 1.
Short direct memory
0
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User’s Manual U18172EJ3V0UD