Hyundai Micro Electronics
GMS81C2020/GMS81C2120
11.5 Addressing Mode
The GMS87C1404 and GMS87C1408 uses six addressing
modes;
(3) Direct Page Addressing → dp
In this mode, a address is specified within direct page.
Example;
• Register addressing
C535
LDA
35H
;A ←RAM[35H]
• Immediate addressing
• Direct page addressing
• Absolute addressing
• Indexed addressing
0035
H
data
À
~
~
~
data → A
~
þ
• Register-indirect addressing
0F550
0F551
C5
35
H
H
(1) Register Addressing
Register addressing accesses the A, X, Y, C and PSW.
(2) Immediate Addressing → #imm
(4) Absolute Addressing → !abs
In this mode, second byte (operand) is accessed as a data
immediately.
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.
With 3 bytes command, it is possible to access to whole
memory area.
Example:
0435
ADC
#35H
MEMORY
ADC, AND, CMP, CMPX, CMPY, EOR, LDA, LDX,
LDY, OR, SBC, STA, STX, STY
04
35
A+35H+C → A
Example;
0735F0 ADC
!0F035H
;A ←ROM[0F035H]
0F035
data
H
H
À
E45535 LDM
35H,#55H
~
~
~
~
A+data+C → A
þ
0F100
0F101
0F102
07
35
F0
H
H
address: 0F035
0035
H
data
data ← 55H
~
~
~
~
þ
H
À
0F100
E4
55
35
0F101
0F102
H
H
Nov. 1999 Ver 0.0
preliminary
39
HYNIX [ HYNIX SEMICONDUCTOR ]
