GMS81C2020 Datasheet, PDF (41/92 Pages) Hynix Semiconductor – CMOS Single-Chip 8-Bit Microcontroller with A/D Converter & VFD Driver

Hyundai Micro Electronics
GMS81C2020/GMS81C2120
Y indexed direct page (8 bit offset) → dp+Y
This address value is the second byte (Operand) of com-
mand plus the data of Y-register, which assigns Memory in
Direct page.
This is same with above (2). Use Y register instead of X.
Y indexed absolute → !abs+Y
Sets the value of 16-bit absolute address plus Y-register
data as Memory. This addressing mode can specify mem-
ory in whole area.
Example; Y=55_H
D500FA LDA !0FA00H+Y
3F35 JMP [35H]
35_H
36_H
~~
0E30A_H
~~
0FA00_H
0A
E3
NEXT
3F
35
~~ ^{À jump to address 0E30AH}
~~
þ
0F100_H
0F101_H
0F102_H
~~
0FA55_H
D5
00
FA
data
þ
0FA00H+55H=0FA55H
~~
À
data → A
Ã
(6) Indirect Addressing
Direct page indirect → [dp]
Assigns data address to use for accomplishing command
which sets memory data(or pair memory) by Operand.
Also index can be used with Index register X,Y.
JMP, CALL
Example;
X indexed indirect → [dp+X]
Processes memory data as Data, assigned by 16-bit pair
memory which is determined by pair data
[dp+X+1][dp+X] Operand plusX-register data in Direct
page.
ADC, AND, CMP, EOR, LDA, OR, SBC, STA
Example; X=10_H
1625 ADC [25H+X]
35_H
05
36_H
E0
~~
0E005_H
data
~~
0FA00_H
16
25
~~ ^{À 0E005H}
þ 25 + X(10) = 35H
~~
à A + data + C → A
Nov. 1999 Ver 0.0
preliminary
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