GMS81C2020 Datasheet, PDF (28/92 Pages) Hynix Semiconductor – CMOS Single-Chip 8-Bit Microcontroller with A/D Converter & VFD Driver

GMS81C2020/GMS81C2120
Hyundai Micro Electro nics
11.2 Program Memory
A 16-bit program counter is capable of addressing up to
64K bytes, but these devices have 20K/12K bytes program
memory space only physically implemented. Accessing a
location above FFFF_H will cause a wrap-around to 0000_H.
Figure 11-4 , shows a map of Program Memory. After re-
set, the CPU begins execution from reset vector which is
stored in address FFFE_H and FFFF_H as shown in Figure
11-5 .
As shown in Figure 11-4 , each area is assigned a fixed lo-
cation in Program Memory. Program Memory area con-
tains the user program.
B000H
GMS81C2020
D000H
GMS81C2012
FEFFH
FF00H
FFC0H
FFDFH
FFE0H
FFFFH
TCALL
AREA
INTERRUPT
VECTOR AREA
PROGRAM
MEMORY
PCALL
AREA
Figure 11-4 Program Memory Map
Page Call (PCALL) area contains subroutine program to
reduce program byte length by using 2 bytes PCALL in-
stead of 3 bytes CALL instruction. If it is frequently called,
it is more useful to save program byte length.
Table Call (TCALL) causes the CPU to jump to each
TCALL address, where it commences the execution of the
service routine. The Table Call service area spaces 2-byte
for every TCALL: 0FFC0_H for TCALL15, 0FFC2_H for
TCALL14, etc., as shown in Figure 11-6 .
Example: Usage of TCALL
LDA
#5
TCALL 0FH
:
:
;
;TABLE CALL ROUTINE
;
FUNC_A: LDA LRG0
RET
;
FUNC_B: LDA LRG1 ₂
RET
;
;TABLE CALL ADD. AREA
;
ORG 0FFC0H
DW FUNC_A
DW FUNC_B
;1BYTE INSTRUCTION
;INSTEAD OF 3 BYTES
;NORM AL CALL
1
;TCALL ADDRESS AREA
The interrupt causes the CPU to jump to specific location,
where it commences the execution of the service routine.
The External interrupt 0, for example, is assigned to loca-
tion 0FFFA_H. The interrupt service locations spaces 2-byte
interval: 0FFF8_H and 0FFF9_H for External Interrupt 1,
0FFFA_H and 0FFFB_H for External Interrupt 0, etc.
As for the area from 0FF00_H to 0FFFF_H, if any area of
them is not going to be used, its service location is avail-
able as general purpose Program Memory.
Address
Vector Area Memory
0FFE0_H
-
E2
-
E4 Serial Peripheral Interface Interrupt Vector Area
E6
Basic Interval Interrupt Vector Area
E8
Watchdog Timer Interrupt Vector Area
EA
A/D Converter Interrupt Vector Area
EC
-
EE
-
F0
-
F2
-
F4
Timer/Counter 1 Interrupt Vector Area
F6
Timer/Counter 0 Interrupt Vector Area
F8
External Interrupt 1 Vector Area
FA
External Interrupt 0 Vector Area
FC
-
FE
RESET Vector Area
NOTE:
"-" means reserved area.
Figure 11-5 Interrupt Vector Area
28
preliminary
Nov. 1999 Ver 0.0