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W742C814

4-BIT MICROCONTROLLER

Winbond 

W742C814

6.4 Data Memory (RAM)

6.4.1 Architecture

The static data memory (RAM) used to store data is arranged as 1024 × 4 bits. The data RAM is

divided into eight banks; each bank has 128 × 4 bits. Executing the MOV DBKR, WR or MOV DBKR,

#I instruction can determine which data bank is used. The data memory can be addressed directly or

indirectly. But the data bank must be confirmed firstly; and the page in the data bank will be done in

the indirect addressing mode, too. In indirect addressing mode, each data bank will be divided into

eight pages. Before the data memory is addressed indirectly, the page which the data memory is in

must be confirmed. The organization of the data memory is shown in Figure 6-2.

1024

addresses

000H

:

07FH

080H

:

0FFH

4 bits

1st data bank

(or Working Registers bank)

2nd data bank

(or Working Registers bank)

3rd data bank

380H

:

3FFH

:

:

8th data bank

1024 * 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 6-2 Data Memory Organization

The 1st and 2nd data bank (00H to 7FH & 80H to FFH) 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 WR, the others can be used as the normal data memory. The WR page

can be switched by executing the MOV WRP, R or MOV WRP, #I instruction. The data memory

cannot operate directly with immediate data, but the WR can do. The relationship between data

memory locations and the page register (PAGE) in indirect addressing mode is described in the next

sub-section.

6.4.2 Page Register (PAGE)

The page register is organized as a 4-bit binary register. The bit descriptions are as follows:

3

2

1

0

PAGE

R/W R/W R/W

Note: R/W means read/write available.

Publication Release Date: February 12, 2003

-9-

Revision A2

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