EM73201
4-BIT MICRO-CONTROLLER FOR GENERAL PURPOSE PRODUCT
FUNCTION DESCRIPTIONS
PROGRAM ROM ( 2K X 8 bits )
2 K x 8 bits program ROM contains user's program and some fixed data .
The basic structure of program ROM can be divided into 5 parts.
1. Address 000h: Reset start address.
2. Address 002h - 00Ch: 4 kinds of interrupt service rountine entry addresses .
3. Address 00Eh-086h : SCALL subroutine entry address, only available at 00Eh,016h,01Eh,026h, 02Eh,
036h, 03Eh, 046h, 04Eh, 056h, 05Eh, 066h, 06Eh, 076h ,07Eh, 086h .
4. Address 000h - 7FFh : LCALL subroutine entry address
5. Address 7E0h - 7FFh : The data region for 5-to-8 bits data conversion table .
6. Address 000h - 7FFh : Except used as above function, the other region can be used as user's program region.
address
000h
002h
004h
006h
008h
00Ah
00Ch
00Eh
086h
2048 x 8 bits
Reset start address
INT0; External interrupt service routine entry address
TRGA, Timer/counterA interrupt service routine entry address
TBI; Time base interrupt service routine entry address
INT1; External interrupt service routine entry address
SCALL, subroutine call entry address
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7FFh
User's program and fixed data are stored in the program ROM. User's program is according the PC value
to send next executed instruction code. Fixed data can be read out by two ways.
(1) Table-look-up instruction:
Table-look-up instruction is depended on the Data Pointer ( DP ) to indicate to ROM address, then to get
the ROM code data.
LDAX
LDAXI
Acc ← ROM[DP]L
Acc ← ROM[DP]H,DP+1
DP is a 12-bit data register which can store the program ROM address to be the pointer for the ROM
code data. First, user load ROM address into DP by instruction "STADPL, STADPM, STADPH",
then user can get the lower nibble of ROM code data by instruction "LDAX" and higher nibble by
instruction "LDAXI".
PROGRAM EXAMPLE: Read out the ROM code of address 777h by table-look-up instruction.
LDIA #07h;
STADPL
; [DP]L ← 07h
STADPM ; [DP]M ← 07h
STADPH
:
; [DP]H ← 07h, Load DP=777h
LDL #00h;
LDH #03h;
LDAX
; ACC ← 6h
* This specification are subject to be changed without notice.
7.20.1999
4
ELAN [ ELAN MICROELECTRONICS CORP ]
