NEC PD75402A Manuale Utente
CHAPTER 3. FEATURES OF ARCHITECTURE AND MEMORY MAP
24
3.1.2
Data Memory Addressing Modes
In the
µ
PD75402A, the 6 types of addressing modes listed on Table 3-2 are available for the data memory space
for efficient addressing per the bit length of the data to be processed.
Also in the
µ
PD75402A, the memory bank to be accessed is fixed by the addressing mode unlike in other products
of the 75X series. So programming is possible without caring about memory bank switching.
(1)
1-bit direct addressing (mem.bit)
An addressing mode to specify each bit of the whole data memory space directly by the instruction’s operand.
The specified memory bank (MB) is MB = 0 if the address specified by the operand is 00H to 3FH and MB = 15
if it is 80H to FFH. Consequently, all the bits in both the static RAM area of 000H to 03FH and the peripheral hardware
area of FF0H to FFFH are addressable. In the peripheral hardware area, however, the bits capable of 1-bit
manipulation are limited (see Table 3-2).
This addressing mode is applied to the 4 instructions of the bit set and reset instructions (SET1, CLR1) and
testinstructions (SKT, SKF).
Example
Set FLAG1, reset FLAG2 and test whether FLAG3 is 0 or not.
FLAG1
EQU
03FH.1
; Address 3FH, bit 1
FLAG2
EQU
027H.2
; Address 27H, bit 2
FLAG3
EQU
017H.0
; Address 17H, bit 0
SET1
FLAG1
; FLAG
←
1
CLR1
FLAG2
; FLAG
←
0
SKF
FLAG3
; FLAG = 0?
(2)
4-bit direct addressing (mem)
An addressing mode to specify the whole data memory space directly by the instruction’s operand per 4 bits.
The specified memory bank (MB) is MB = 0 if the address specified by the operand is 00H to 3FH and MB = 15
if it is 80H to FFH. Consequently, both the static RAM area of 000H to 03FH and the peripheral hardware area of FF0H
to FFFH are addressable.
This addressing mode is applied to the MOV, XCH, INCS, IN, and OUT instructions.
Example
1.
Input Port 2 and store it in “DATA1”.
DATA1
EQU
2FH
; “DATA1” is at address 2FH
IN
A, PORT 2
; A
←
Port 2
MOV
DATA1, A
; (DATA1)
←
A
2.
Output the data of “BUFF” to Port 5.
BUFF
EQU
01AH
; “BUFF” is at address 01AH
MOV
A, BUFF
; A
←
(BUFF)
OUT
PORT 5, A
; PORT 5
←
A