S3C72P9 datasheet(26/225 Pages) SAMSUNG

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ADDRESS SPACES

S3C72P9/P72P9 (Preliminary Spec)

2-14

+ PROGRAMMING TIP — Selecting the Working Register Area

The following examples show the correct programming method for selecting working register area:

1. When ERB = "0":

VENT2

1,0,INT0

; EMB

← 1, ERB ← 0, Jump to INT0 address

;

INT0

PUSH

; PUSH current SMB, SRB

SRB

; Instruction does not execute because ERB = "0"

PUSH

; PUSH HL register contents to stack

PUSH

; PUSH WX register contents to stack

PUSH

; PUSH YZ register contents to stack

PUSH

; PUSH EA register contents to stack

SMB

EA,#00H

80H,EA

HL,#40H

INCS

WX,EA

YZ,EA

POP

; POP EA register contents from stack

POP

; POP YZ register contents from stack

POP

; POP WX register contents from stack

POP

; POP HL register contents from stack

POP

; POP current SMB, SRB

IRET

The POP instructions execute alternately with the PUSH instructions. If an SMB n instruction is used in an

interrupt service routine, a PUSH and POP SB instruction must be used to store and restore the current SMB and

SRB values, as shown in Example 2 below.

2. When ERB = "1":

VENT2

1,1,INT0

; EMB

← 1, ERB ← 1, Jump to INT0 address

;

INT0

PUSH

; Store current SMB, SRB

SRB

; Select register bank 2 because of ERB = "1"

SMB

EA,#00H

80H,EA

HL,#40H

INCS

WX,EA

YZ,EA

POP

; Restore SMB, SRB

IRET

S3C72P9 Datasheet(PDF) 26 Page - Samsung semiconductor

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