NAME
	CAS2 --Compare and swap (two-operand)	(68020+)

SYNOPSIS
	CAS2	Dc1:Dc2,Du1:Du2,(Rn1):(Rn2)

	Size = (Word, Long)

FUNCTION
	This instruction is a read-modify-write instruction and should
	NEVER be used on Amiga because of conflicts with customs chips
	Destination operand 1, which is in memory to specified address by
	(Rn1), is compared to data register Dc1. If there's equality (Z=1),
	destination operand 2, which is in memory to specified address by
	(Rn2), is compared to data register Dc2.

	If there's equality (Z=1), destination operand 1 can be updated, i.e.
	new operand Du1 (Data Update) is moved in destination (Rn1).

	And also, destination operand 2 can be updated, i.e. new operand Du2
	(Data Update) is moved in destination (Rn2).

	If there's no equality (Z=0), reference registers Dc1 and Dc2 have to
	be updated. So there's move from destination operand (Rn1) in Dc1, and
	from (Rn2) in Dc2.

FORMAT
	------------------------------------------------------------------
	| 15 |14 |13 |12 |11 |10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
	|----|---|---|---|---|-------|---|---|---|---|---|---|---|---|---|
	| 0  | 0 | 0 | 0 | 1 | SIZE  | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 0 |
	|----|-----------|---|-------|-----------|---|---|---|-----------|
	|D/A1|  Rn1 REG. | 0 | 0 | 0 |  Du1 REG. | 0 | 0 | 0 |  Dc1 REG. |
	|----|-----------|---|---|---|-----------|---|---|---|-----------|
	|D/A2|  Rn2 REG. | 0 | 0 | 0 |  Du2 REG. | 0 | 0 | 0 |  Dc2 REG. |
	------------------------------------------------------------------

SIZE
	10->one Word operation
	11->one Long operation

REGISTER
	D/A1 = 0: Rn1=Dn
	D/A1 = 1: Rn1=An
	D/A2 = 0: Rn2=Dn
	D/A2 = 1: Rn2=An

	Du1, Du2 registers: indicates number of data register, which contains
	the new value to update in destination operand.

	Dc1, Dc2 registers: indicates number of data register, which contains
	the reference value to compare to destination operand.

	Rn1, Rn2 registers: indicates number of destination registers.

RESULT
	X - not affected
	N - Set following to comparisons results.
	Z - Set if the result of comparisons is zero. Cleared otherwise.
	V - Set if overflow. Cleared otherwise.
	C - Set if carry. Cleared otherwise.

SEE ALSO
	CAS