Apple II manual Store DOUBLE-BYTE Indirect, Store POP Indirect

STORE DOUBLE-BYTE INDIRECT:

STD @Rn [ 7n ]

The low-order ACC byte is stored into memory location whose address resides in Rn, and Rn is the incremented by 1. The high-order ACC byte is stored into the memory location whose address resides in the incremented Rn, and Rn is again incremented by 1. Branch conditions reflect the ACC contents which are not disturbed. The carry is cleared.

EXAMPLE:

15	34	A0	SET	R5	$A034	;Load pointers			R5, R6
16	22	90	SET	R6	$9022	;with $A034 and $9022
65			LDD	@R5		;Move	double	byte from
76			STD	@R6		;$A034-35 to		$9022-23.
						;Both	pointers		incremented by 2.

POP INDIRECT:

POP @Rn [ 8n ]

The low-order ACC byte is loaded from the memory location whose address resides in Rn after Rn is decremented by 1, and the high order ACC byte is cleared. Branch conditions reflect the final 2-byte ACC contents which will always be positive and never minus one. The carry is cleared. Because Rn is decremented prior to loading the ACC, single byte stacks may be implemented with the ST @Rn and POP @Rn ops (Rn is the stack pointer).

EXAMPLE:

15	34	A0	SET	R5	$A034	;Init stack pointer
10	04	00	SET	R0	4	;Load 4 into ACC
55			ST	@R5		;Push 4 onto stack
10	05	00	SET	R0	5	;Load 5 into ACC
55			ST	@R5		;Push 5 onto stack
10	06	00	SET	R0	6	;Load 6 into ACC
55			ST	@R5		;Push 6 onto stack
85			POP	@R5		;Pop 6	off stack into ACC
85			POP	@R5		;Pop 5	off stack
85			POP	@R5		;Pop 4	off stack

STORE POP INDIRECT:

STP @Rn [ 9n ]

The low-order ACC byte is stored into the memory location whose address resides in Rn after Rn is decremented by 1. Branch conditions will reflect the 2-byte ACC contents which are not modified. STP @Rn and POP @Rn are used together to move data blocks beginning at the greatest address and working down. Additionally, single-byte stacks may be implemented with the STP @Rn ops.