NEC PD75402A Manuale Utente

The data memory consists of the data and peripheral hardware areas as shown in Fig. 4-3.

The 

µ

PD75402A’s data area consists of the static RAM (64 words 

×

 4 bits). The data area is used to store processing

data and is operated by the memory manipulation instruction.

The static RAM is mapped to Memory bank 0 by 64 

×

 4 bits. While Bank 0 is mapped as the data area, it is also

available as the general register area (000H to 003H) and the stack area (020H to 03FH).

In the static RAM, 1 address consists of 4 bits. It is possible either to operate per 8 bits by the 8-bit memory

manipulation instruction or to operate per bit by the bit manipulation instruction, however. In the 8-bit manipulation

instruction, an even address should be specified.

Operation is possible either by the general register manipulation instruction or by the memory manipulation

instruction. Up to four 4-bit registers are available. Of the 4 general registers, that part which is not used in the

program is available as the data area (see 4.4 “GENERAL REGISTER”).

The stack area is set by an instruction and is available as the save area at the subroutine or interrupting process

execution (see 4.6 “STACK POINTER”). In that case, the stack area is at the static RAM’s addresses 020H to 03FH.

Data Memory

Memory Bank

Bank 0

(64 

×

 4)

(4 

×

 4)

(32 

×

 4)

128 

×

 4

Not built in.

0 0 0 H

0 0 3 H

0 0 4 H

0 2 0 H

0 3 F H

F 8 0 H

F F F H

General
Register Area

Data Area
Static RAM
  (64 

×

 4)

Bank 15

Stack Area

Peripheral
Hardware
Area