HYUNDAI MicroElectronics
GMS81C2012/GMS81C2020
8.4 Addressing Mode
The GMS800 series MCU uses six addressing modes;
• Register addressing
(3) Direct Page Addressing → dp
In this mode, a address is specified within direct page.
Example; G=0
• Immediate addressing
C535
LDA
35H
;A ←RAM[35H]
• Direct page addressing
• Absolute addressing
• Indexed addressing
35H
data
• Register-indirect addressing
➋
~
~
~
data → A
~
➊
0E550H
0E551H
C5
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(1) Register Addressing
Register addressing accesses the A, X, Y, C and PSW.
(2) Immediate Addressing → #imm
In this mode, second byte (operand) is accessed as a data
immediately.
(4) Absolute Addressing → !abs
Example:
Absolute addressing sets corresponding memory data to
Data, i.e. second byte (Operand I) of command becomes
lower level address and third byte (Operand II) becomes
upper level address.
0435
ADC
#35H
MEMORY
With 3 bytes command, it is possible to access to whole
memory area.
04
35
A+35H+C → A
ADC, AND, CMP, CMPX, CMPY, EOR, LDA, LDX,
LDY, OR, SBC, STA, STX, STY
Example;
0735F0 ADC
!0F035H
;A ←ROM[0F035H]
When G-flag is 1, then RAM address is defined by 16-bit
address which is composed of 8-bit RAM paging register
(RPR) and 8-bit immediate data.
0F035H
data
➋
Example: G=1
~
~
~
~
A+data+C → A
E45535 LDM
35H,#55H
➊
0F100H
0F101H
0F102H
07
35
F0
address: 0F035
0135H
data
data ¨ 55H
~
~
~
~
The operation within data memory (RAM)
ASL, BIT, DEC, INC, LSR, ROL, ROR
➊
0F100H
➋
E4
55
35
Example; Addressing accesses the address 0135H regard-
less of G-flag.
0F101H
0F102H
MAR. 2000 Ver 1.00
35
HYNIX [ HYNIX SEMICONDUCTOR ]
