W742C813 Datasheet, PDF (9/56 Pages) Winbond – 4 BIT MICROCONTROLLER

W742E/C813
5.3 Program Memory (ROM)
The read-only memory (ROM) is used to store program codes or the look-up table that can be
arranged up to 65536(64K) × 4 bits. The program ROM is divided into sixteen pages; the size of each
page is 2048(2K) × 16 bits. So the total ROM size is 32768(32K) × 16 bits. Before the jump or
subroutine call instructions are to be executed, the destination ROM page register (ROMPR) must be
determined firstly. The ROM page can be selected by executing the MOV ROMPR, #I or MOV
ROMPR,RAM instructions. But the branch decision instructions (e.g. JB0, SKB0, JZ, JC, ...) must jump
into the same ROM page. The look-up table area is allocated in lower half part of ROM (PC:
4000H to 7FFFH). Each look-up table element is composed of 4 bits, so the look-up table can be
addressed up to 65536(64K) elements. It uses instructions MOV TAB0,R MOV TAB1,R MOV
TAB2,R MOV TAB3,R to determine the look-up table element address. The look-up table address is
4 times PC counter, and the offset value is 4000H. Instruction MOVC R is used to read the look-up
table content and save data into the RAM. The organization of the program memory is shown in Figure
5-1.
0000H
:
07FFH
0800H
:
0FFFH
1000H
:
17FFH
1800H
:
1FFFH
2000H
:
27FFH
2800H
:
2FFFH
3000H
:
37FFH
3800H
:
3FFFH
16 bits
Page 0
Page 1
Page 2
Page 3
Page 4
Page 5
Page 6
Page 7
16384 * 16 bits
4000H
:
47FFH
4800H
:
4FFFH
5000H
:
57FFH
5800H
:
5FFFH
6000H
:
67FFH
6800H
:
6FFFH
7000H
:
77FFH
7800H
:
7FFFH
16 bits
Page 8
:
:
Page A
:
:
Page C
:
:
Page E
:
:
16384 * 16 bits
Each element (4 bits)
of the look-up table
Page 9
Page B
Page D
Page F
All Program memory can be used to store instruction code,
but the look-up table just can be stored in the lower half ROM (4000H~7FFFH).
Figure 5-1 Program Memory Organization
Publication Release Date: December 2000
-9-
Revision A1