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Assembler

LSL, LSR -- Logical shift left and logical shift right

SYNOPSIS

LSd	Dx,Dy
LSd	#<data>,Dy
LSd	<ea>

where d is direction, L or R
Size = (Byte, Word, Long)

FUNCTION

Shift the bits of the operand in the specified direction. The carry bit set set to the last bit shifted out of the operand. The shift count for the shifting of a register may be specified in two different ways:

Immediate - the shift count is specified in the instruction (shift range 1-8).
Register - the shift count is contained in a data register specified in the instruction (shift count mod 64)

For a register, the size may be byte, word, or long, but for a memory location, the size must be a word. The shift count is also restricted to one for a memory location.

LSL:		<--
	C<------	OPERAND	<---	0
		\|
		\|	(V = 0)
	X<---'

LSR:
	-->
0 --->	OPERAND	-------> C
		\|
		\|
		`---> X

FORMAT

In the case of the shifting of a register:

15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
1	1	1	0	NUMBER / REGISTER			dr	SIZE	i/r	0	1	REGISTER

In the case of the shifting of a memory area:

15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
1	1	1	0	0	0	1	dr	1	1	MODE			REGISTER
										<ea>

NUMBER/REGISTER

Specifies number of shifting or number of register which contents the number of shifting.
If i/r = 0, number of shifting is specified in the instruction as immediate data
If i/r = 1, it's specified in the data register.
If dr = 0, right shifting
If dr = 1, left shifting

SIZE

00	->	one Byte operation
01	->	one Word operation
10	->	one Long operation

For a register shifting:
<ea> Indicates the number of data register on which shifting is applied.
For a memory shifting:
<ea> indicates operand which should be shifted.
Only addressing modes relatives to memory are allowed:

Addressing Mode	Mode	Register
Dn	-	-
An	-	-
(An)	010	No reg. An
(An)+	011	No reg. An
-(An)	100	No reg. An
(d16,An)	101	No reg. An
(d8,An,Xi)	110	No reg. An
(bd,An,Xi)<	110	No reg. An
([bd,An,Xi]od)	110	No reg. An
([bd,An],Xi,od)	110	No reg. An

Addressing Mode	Mode	Register
Abs.W	111	000
Abs.L	111	001
(d16,PC)	-	-
(d8,PC,Xi)	-	-
(bd,PC,Xi)	-	-
([bd,PC,Xi],od)	-	-
([bd,PC],Xi,od)	-	-
#data	-	-

RESULT

X	-	Set according to the last bit shifted out of the operand.
N	-	Set if the result is negative. Cleared otherwise.
Z	-	Set if the result is zero. Cleared otherwise.
V	-	Always cleared
C	-	Set according to the last bit shifted out of the operand.

English version not yet available.

Änderungen und Irrtümer vorbehalten. Letzte Änderung:
23 März 2004.
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