* TTL FAST FLOATING POINT ASCII ROUND ROUTINE (FFPARND) **************************************** * (C) COPYRIGHT 1981 BY MOTOROLA INC. * **************************************** *********************************************** * FFPARND * * ASCII ROUND SUBROUTINE * * * * THIS ROUTINE IS NORMALLY CALLED AFTER THE * * 'FFPFPA' FLOAT TO ASCII ROUTINE AND ACTS * * UPON ITS RESULTS. * * * * INPUT: D6 - ROUNDING MAGNITUDE IN BINARY * * AS EXPLAINED BELOW. * * D7 - BINARY REPRESENTATION OF THE * * BASE 10 EXPONENT. * * SP -> RETURN ADDRESS AND OUTPUT * * FROM FFPFPA ROUTINE * * * * OUTPUT: THE ASCII VALUE ON THE STACK IS * * CORRECTLY ROUNDED * * * * THE CONDITION CODES ARE UNDEFINED * * * * ALL REGISTERS TRANSPARENT * * * * THE ROUNDING PRECISION REPRESENTS THE * * POWER OF TEN TO WHICH THE ROUNDING WILL * * OCCUR. (I.E. A -2 MEANS ROUND THE DIGIT* * IN THE HUNDREDTH POSITION FOR RESULTANT * * ROUNDING TO TENTHS.) A POSITIVE VALUE * * INDICATES ROUNDING TO THE LEFT OF THE * * DECIMAL POINT (0 IS UNITS, 1 IS TENS * * E.T.C.) * * * * THE BASE TEN EXPONENT IN BINARY IS D7 * * FROM THE 'FFPFPA' ROUTINE OR COMPUTED BY* * THE CALLER. * * * * THE STACK CONTAINS THE RETURN ADDRESS * * FOLLOWED BY THE ASCII NUMBER AS FROM * * THE 'FFPFPA' ROUTINE. SEE THE * * DESCRIPTION OF THAT ROUTINE FOR THE * * REQUIRED FORMAT. * * * * EXAMPLE: * * * * INPUT PATTERN '+.98765432+01' = 9.8765432 * * * * ROUND +1 IS +.00000000+00 = 0. * * ROUND 0 IS +.10000000+02 = 10. * * ROUND -1 IS +.10000000+02 = 10. * * ROUND -2 IS +.99000000+01 = 9.9 * * ROUND -3 IS +.98800000+01 = 9.88 * * ROUND -6 IS +.98765400+01 = 9.87654 * * * * NOTES: * * 1) IF THE ROUNDING DIGIT IS TO THE LEFT * * OF THE MOST SIGNIFICANT DIGIT, A ZERO* * RESULTS. IF THE ROUNDING DIGIT IS TO* * THE RIGHT OF THE LEAST SIGNIFICANT * * DIGIT, THEN NO ROUNDING OCCURS * * 2) ROUNDING IS HANDY FOR ELIMINATING THE* * DANGLING '999...' PROBLEM COMMON WITH* * FLOAT TO DECIMAL CONVERSIONS. * * 3) POSITIONS FROM THE ROUNDED DIGIT AND * * TO THE RIGHT ARE SET TO ZEROES. * * 4) THE EXPONENT MAY BE AFFECTED. * * 5) ROUNDING IS FORCED BY ADDING FIVE. * * 6) THE BINARY EXPONENT IN D7 MAY BE * * PRE-BIASED BY THE CALLER TO PROVIDE * * ENHANCED EDITING CONTROL. * * 7) THE RETURN ADDRESS IS REMOVED FROM * * THE STACK UPON EXIT. * *********************************************** PAGE *FFPARND IDNT 1,1 FFP ASCII ROUND SUBROUTNE * OPT PCS XDEF FFPARND ENTRY POINT FFPARND MOVEM.L D7/A0,-(SP) SAVE WORK ON STACK SUB.W D6,D7 COMPUTE ROUNDING DIGIT OFFSET BLE.S FAFZRO BRANCH IF LARGER THAN VALUE CMP.W #8,D7 INSURE NOT PAST LAST DIGIT BHI FARTN RETURN IF SO LEA 8+4+1(SP,D7),A0 POINT TO ROUNDING DIGIT CMP.B #'5',(A0) ? MUST ROUNDUP BCC.S FADORND YES, ROUND SUBQ.W #1,D7 ? ROUND LEADING DIGIT ZERO (D7=1) BNE.S FAZEROL NO, ZERO IT OUT FAFZRO LEA 8+4+2(SP),A0 FORCE ZEROES ALL THE WAY ACROSS MOVE.L #'E+00',8+4+10(SP) FORCE ZERO EXPONENT MOVE.B #'+',8+4(SP) ZERO IS ALWAYS POSITIVE BRA.S FAZEROL ZERO MANTISSA THEN RETURN * ROUND UP MUST OCCUR FADORND MOVE.L A0,-(SP) SAVE ZERO START ADDRESS ON STACK FACARRY CMP.B #'.',-(A0) ? HIT BEGINNING BEQ.S FASHIFT YES, SHIFT DOWN ADDQ.B #1,(A0) LOOK AT NEXT CHARACTER CMP.B #'9'+1,(A0) ? PAST NINE BNE.S FAZERO NO, NOW ZERO THE END MOVE.B #'0',(A0) FORCE ZERO FOR OVERFLOW BRA.S FACARRY LOOP FOR CARRY * OVERFLOW PAST TOP DIGIT - SHIFT RIGHT AND UP EXPONENT FASHIFT ADDQ.L #1,(SP) ZERO PAD STARTS ONE LOWER NOW ADDQ.L #1,A0 BACK TO LEADING DIGIT MOVEQ #$31,D7 DEFAULT FIRST DIGIT ASCII ONE SWAP.W D7 INITIALIZE OLD DIGIT MOVE.B (A0),D7 PRE-LOAD CURRENT DIGIT FASHFTR SWAP.W D7 TO PREVIOUS DIGIT MOVE.B D7,(A0)+ STORE INTO THIS POSITION MOVE.B (A0),D7 LOAD UP NEXT DIGIT CMP.B #'E',D7 ? THE END BNE.S FASHFTR NO, SHIFT ANOTHER TO THE RIGHT * INCREMENT EXPONENT FOR SHIFT RIGHT CMP.B #'+',1(A0) ? POSITIVE EXPONENT ADDQ.L #3,A0 POINT TO LEAST EXP DIGIT BNE.S FANGEXP BRANCH NEGATIVE EXPONENT ADDQ.B #1,(A0) ADD ONE TO EXPONENT CMP.B #'9'+1,(A0) ? OVERFLOW PAST NINE BNE.S FAZERO NO, NOW ZERO SUB.B #10,(A0) ADJUST BACK V1.4/V1.5 ADDQ.B #1,-(A0) CARRY TO NEXT DIGIT BRA.S FAZERO AND NOW ZERO END FANGEXP CMP.W #'01',-1(A0) ? GOING FROM 1 TO +0 BNE.S FANGOK BRANCH IF NO MOVE.B #'+',-2(A0) CHANGE MINUS TO PLUS FANGOK SUBQ.B #1,(A0) SUBTRACT ON FROM EXPONENT CMP.B #'0'-1,(A0) ? UNDERFLOW BELOW ZERO BNE.S FAZERO NO, ZERO REMAINDER ADD.B #10,(A0) ADJUST BACK V1.4 SUBQ.B #1,-(A0) BORROW FROM NEXT DIGIT * ZERO THE DIGITS PAST PRECISION REQUIRED FAZERO MOVE.L (SP)+,A0 RELOAD SAVED PRECISION FAZEROL CMP.B #'E',(A0) ? AT END BEQ.S FARTN BRANCH IF SO MOVE.B #'0',(A0)+ ZERO NEXT DIGIT BRA.S FAZEROL AND TEST AGAIN * RETURN TO THE CALLER FARTN MOVEM.L (SP)+,D7/A0 RESTORE REGISTERS RTS RETURN END