Systems Reference Library - All about the IBM 1130 Computing ...

BRANCH OR SKIP ON CONDITION (BSC OR BOSC) Branch FunctionFORMAT0 OP F T I A B O Cond 15 0 Address 151 0 1 1 1 0 1 0 1 111 1 . 1 1 1 1 1 1 1 I 1 1 I 1 1 1 I I I l 1 1 1 1 I I4 C–F X X X X X X117191 BIDESCRIPTIONThis long format instruction performs in a manner similarto the short format (skip function) BSC or BOSCinstruction in that the same six conditions associatedwith the accumulator (A) can be tested. Conditions tobe tested are specified in the same manner as the shortBSC or BOSC instruction described on the precedingpage.If one or more of the specified conditions are true,the next instruction in sequence is executed. If none ofthe specified conditions is true, a branch is made tothe core-storage location specified by the effective address(EA) of the instruction. If no conditions are specifiedin this instruction, a branch to the EA alwaysoccurs. Note that this is reverse logic from the shortformat (skip function) BSC or BOSC instruction.If bit position 9 of the instruction is 1, the instructionis called a branch out of interrupt (BOSC) instruction.A long format (branch function) BOSC performsthe same branch functions as described in the precedingparagraphs, and also resets the highest priority interruptlevel that is on if a branch occurs.The long format (branch function) BSC or BOSC instructioncan be used to return to a mainline programfrom a subroutine (bit position 9 should be 0) or interruptroutine (bit position 9 should be 1). This isaccomplished by making the EA of the BSC or BOSCinstruction identical to the EA of a previously executedBSI instruction.Some branch condition examples as compared to skipcondition examples are shown in the table on the precedingpage.THE CARRY INDICATOR is not reset when tested bythis instruction.THE OVERFLOW INDICATOR is reset when testedby this instruction.I EXAMPLESAssembler Language CodingEquivalent Machine Language InstructionLabel21 25Operation F T27 30 3233 35 40SeeNoteHexadecimalValueDescriptionFormat1 1 1 B I S I C I L AD ID IR1 , IC 101N ID 1 3 4C*XXIOCX Branch to CSL at EA (Addy) on no condition true Long- I 1 1 I B1S,C, L I A,DIDIRI , ,C IOINID 1 3 o•xxxxx Branch to CSL at EA (Addr+XRI) on no condition true1 1 I B,S 1 C, L 2 A,D,D,R 1 , I C ,O,N 1 D 1 3 4E*XXXXX Branch to CSL at EA (Addr+XR3) on no condition true1 I I B I S I C, L 3 A,D,D,R 1 ,C,O,N,D 1 3 4F*3000CX Branch to CSL at EA (Addr+XR2) on no condition true1 1 1 BIS I C, I AD ,I) ,R. , ,C,O,N,D 2 3 4C*XXXXX Branch to CSL at EA (V in CSL at Addr) on no condition true1 I I BIS IC I I I AD ,D ji, , ,C 1 0,N,D 2 3 4D*XXXXX Branch to CSL at EA (V in CSL at "Addr+XRI") on no1 1 1 1 1 1 1 i 1 1 i 1 1 1 condition trueI I B , S,C, I AD I D ,R, , ,C ANA, 2 3 4E•0000C Branch to CSL at EA (V in CSL at "Addr+XR2") on no11 I I I i I I I I I I I condition trueI 1 1 B,SICI I 3 A,D,D.R1 IC,O,N,D 12131 4F 5XXXXX Branch to CSL at EA (V in CSL at "Addr+XR3") on noI I 1 1 I I I I I I I I I Icondition trueInstructionDirectAddressingLongInstructionIndirectAddressingM The third from high-order hex. digit can be 0,1,2, or 3, (BSC) or 4,5,6,or 7, (BOSC) depending on which conditions are tested.El The third from high-order hex. digit can be 8, 9, A, or B, (BSC) or C, D, E,or F, (BOSC) depending on which conditions are tested.The highest priority interrupt level on is reset if instruction is BOSC and abranch occurs.42BSC/BOSC