1. xerox 560 computer system - The UK Mirror Service

If the value of the R field is zero, the effective halfwordis tested for being a zero, negative, or positive value.The condition code is set, according to the result of thetest, but the effective halfword is not affected. A memorywrite-protection violation cannot occur in this case; however,a memory read-protection violation can occur.Affected: CC if (1)8-11 = 0; Trap: Fixed-pointoverflow(EH L) and CC if (1)8-11 10If (1)8-11 = 0, test halfword and set CCIf (1)8-11/0, EH + (I)8-11SE -EHL and set CCCondition code settings:2 3 4 Result in EH L- 0 0 Zero- 0 Negative0 Positive- 0 No fixed-point overflowoFixed-point overflowNo carry from halfword- Carry from halfwordIf CC2 is set to 1 and the fixed-point arithmetic trap mask(AM) is a 1, the BP traps to location X'43 1 after the resultis stored in the effective halfword location; otherwise,the BP executes the next instruction in sequence.If MTH is executed in an interrupt or trap location, thecondition code is not affected and a 20-bit reference addressis used, as described under "Interrupt and Trap EntryAddressing", Chapter 2.MTWMODIFY AND TEST WORD t(Word index alignment)If the value of the R field is nonzero, the high-order bitof the R field (bit position 8 of the instruction word) isextended 28 bit positions to the left, to form a word withbit positions 0-27 of that word equal to the high-order bitof the R field. This word is added to the effective wordand then (if no memory protection violation occurs) thesum is stored in the effective word location and conditioncode is set according to the value of the resultant word.The sum is stored regardless of whether or not overflowoccurs. This process allows modification of a word byany number in the range -8 through +7, followed bya test.If the value of the R field is zero, the effective word istested for being a zero, negative, or positive value. Thecondition code is set according to the result of the test,but the effective word is not affected. A memory writeprotectionviolation cannot occur in this case; however,a memory read-protection violation can occur.Affected: CC if (1)8-11 = 0;(EWL) and CC if (1)8-11 1 0If (1)8-11 = 0, test word and set CCIf (1)8-11 10, EW + 18-11 SE -Condition code settings:2 3 4 Result in EWL- 0 0 Zero- 0 Negativeo Positive- 0 - - No fixed-point overflow- Fixed-point overflowo - - No carry from word- - - Carry from wordTrap: Fixed-pointoverflowEWL and set CCIf CC2 is set to 1 and the fixed-point arithmetic trap mask(f1to.A\ :c: n 1 +ho RP +rnnc: +1"'1 Il"'Irn+:l"'ln )(1A.11 nf+or +ho rQ-\' .. ,,'/ 'v - II ••• - _ •.• -.-.- ' ___ "_" .... - _ .. _ •... _._suit is stored in the effective word location; otherwise, theBP executes the next instruction in sequence.If MTW is executed in an interrupt or trap location, thecondition code is not affected and a 20-bit reference addressis used, as described under "Interrupt and Trap EntryAddressing ll , Chapter 2.COMPARISON INSTRUCTIONStThis instruction requires two memory references to the samelocation for its execution. To preclude other processorsfrom accessing the effective location during this time, thememory unit containing the effective location is reserved(not accessi bl e to other processors) unti I the i nstructi on iscompleted.The compuri:>on in:)ilu~iiulI:) ure:Instruction NameCompare Immedi ateCompare ByteMnemonicCICB66 Compari son Instructi ons