NAME	CHK2 -- Check register against upper and lower bounds (68020+)
SYNOPSIS	CHK2 <ea>,Rn Size = (Byte, Word, Long)
FUNCTION	<ea> indicates memory area of two bounds: in 1st memory position, lower bound, in 2nd memory position, upper bound. Those two values are adjacent in memory. For signed comparisons, the lowest arithmetic value, expressed as a two complement integer, have to be the lower bound. If Rn is a data register Dn and if size of operation is 8 or 16 bits, only the 8 or 16 bits of low weight of Dn and bounds are taken in count. In opposite, if Rn is an address register An, it must be extension of bounds sign and 32 bits of An are taken care. If Rn is located out of 2 bounds, a CHK instruction, vector number 6, occurs.
FORMAT	<ea> 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 0 0 0 0 0 SIZE 0 1 1 MODE REGISTER D/A REGISTER 1 0 0 0 0 0 0 0 0 0 0 0
REGISTER	Register specifies the register Rn which contains the value to test. If D/A = 0: Rn = Dn If D/A = 1: Rn = An <ea> specifies bounds, addressing modes allowed are: Addressing Mode Mode Register Dn - - An - - (An) 010 No reg. An (An)+ - - -(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) 111 010 (d8,PC,Xi) 111 011 (bd,PC,Xi) 111 011 ([bd,PC,Xi],od) 111 011 ([bd,PC],Xi,od) 111 011 #data - -
SIZE	00 -> one Byte operation 01 -> one Word operation 10 -> one Long operation
RESULT	X - Not affected N - Undefined. Z - Set if Rn is equal to one of the two bounds. Cleared otherwise. V - Undefined. C - Set if Rn is out of bounds. Cleared otherwise.

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