NEC PD75402A, PD75P402 user manual Data Memory Addressing Modes, Bit direct addressing mem.bit

CHAPTER 3. FEATURES OF ARCHITECTURE AND MEMORY MAP

3.1.2Data Memory Addressing Modes

In the μPD75402A, 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 μPD75402A, 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

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