W742E Datasheet, PDF (15/60 Pages) Winbond – 4 BIT MICROCONTROLLER

W742E/C811
5.4 Data Memory (RAM)
5.4.1 Architecture
The static data memory (RAM) used to store data is arranged up to 5120(5K) × 4 bits. The data RAM is
divided into 40 banks; each bank has 128 × 4 bits. Executing the MOV DBKRL,WR,MOV DBKRH,WR
or MOV DBKRL,#I, MOV DBKRH,#I instructions can determine which data bank is used. The data
memory can be accessed directly or indirectly and the data bank register has to be confirmed firstly. In
the indirect addressing mode, each data bank will be divided into eight pages. The RAM page register
has to be setting when in the indirect accessing RAM. The instructions MOV WRn,@WRq MOV
@WRq,WRn could Read or Write the whole memory in the indirect addressing mode. The RAM
address of @WRq indicates to (DBKRH)*800H + (DBKRL)*80H + (RAM page)*10H + (WRq). The
organization of the data memory is shown in Figure 5-2.
4 bits
0000H
:
data bank 00
007FH ^{(or Working Registers bank)}
5120
0080H
:
data bank 01
00FFH ^{(or Working Registers bank)}
address
:
:
:
1380H
:
13FFH
data bank 39
5120 * 4 bits
00H
1st data RAM page
:
(or 1st WR page)
0FH
10H
2nd data RAM page
:
(or 2nd WR page)
1FH
20H
3rd data RAM page
:
(or 3rd WR page)
2FH
:
:
70H
8th data RAM page
:
(or 8th WR page)
7FH
Figure 5-2 Data Memory Organization
The 1st and 2nd data bank (00H to 7FH & 80H to 0FFH) in the data memory can also be used as the
working registers (WR). It is also divided into sixteen pages. Each page contains 16 working registers.
When one page is used as Working Register, the others can be used as the normal data memory. The
WR page register can be switched by executing the MOV WRP,R or MOV WRP,#I instructions. The
data memory can not do the logical operation directly with the immediate data, it has to via the Working
Register.
5.4.2 RAM Page Register (PAGE)
The page register is organized as a 4-bit binary register. The bit descriptions are as follows:
3
PAGE
2
1
0
R/W R/W R/W
Note: R/W means read/write available.
Bit 3 is reserved.
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Publication Release Date: December 2000
Revision A1