Motorola DSP56000 manual Address Register Indirect Postincrement by Offset Nn, Predecrement By

ADDRESSING

EXAMPLE: MOVE X1,X: (R2)+N2

	BEFORE EXECUTION
	X1		X0
47	24	23	0
A 5 B 4 C 6		0	0 0 0 0 1
23	0	23	0

	AFTER EXECUTION
	X1		X0
47	24	23	0
A 5 B 4 C 6		0	0 0 0 0 1
23	0	23	0

X MEMORY

230

$3204 X X X X X X

$3200 X X X X X X

150

R2 $3200

150

N2 $0004

150

M2 $FFFF

X MEMORY

	23						0
$3204	X	X	X		X	X	X
$3200	$	A 5		B	4	C	6
			15				0
		R2			$3204
			15				0
		N2			$0004
			15				0
	M2				$FFFF

Assembler Syntax: (Rn)+Nn

Memory Spaces: P:, X:, Y:, XY:, L:

Additional Instruction Execution Time (Clocks): 0

Additional Effective Address Words: 0

Figure 4-7 Address Register Indirect — Postincrement by Offset Nn

an extra instruction cycle, cannot be used for making XY: memory references.

4.4.1.7Predecrement By 1

The address of the operand is the contents of the address register, Rn, decremented by 1 before the operand address is used (see Table 4-1and Figure 4-10). The contents of Rn are decremented and stored in the same address register. This addressing mode re- quires an extra instruction cycle. This mode cannot be used for making XY: memory references, nor can it be used for modifying the contents of Rn without an associated data

MOTOROLA ADDRESS GENERATION UNIT 4 - 13