* TTL FAST FLOATING POINT FLOAT TO ASCII (FFPFPA) *************************************** * (C) COPYRIGHT 1980 BY MOTOROLA INC. * *************************************** ****************************************************** * FFPFPA * * FLOAT TO ASCII * * * * INPUT: D7 - FLOATING POINT NUMBER * * * * OUTPUT: D7 - THE BASE TEN EXPONENT IN BINARY * * FOR THE RETURNED FORMAT * * SP - DECREMENTED BY 14 AND * * POINTING TO THE CONVERTED * * NUMBER IN ASCII FORMAT * * * * ALL OTHER REGISTERS UNAFFECTED * * * * CONDITION CODES: * * N - SET IF THE RESULT IS NEGATIVE * * Z - SET IF THE RESULT IS ZERO * * V - CLEARED * * C - CLEARED * * X - UNDEFINED * * * * CODE SIZE: 192 BYTES STACK WORK AREA: 42 BYTES * * * * * * {S}{'.'}{DDDDDDDD}{'E'}{S}{DD} * * < FRACTION >< EXPONENT > * * * * WHERE S - SIGN OF MANTISSA OR EXPONENT * * ('+' OR '-') * * D - DECIMAL DIGIT * * * * STACK OFFSET OF RESULT S.DDDDDDDDESDD * * AFTER RETURN 00000000001111 * * 01234567890123 * * * * * * EXAMPLES +.12000000E+03 120 * * +.31415927E+01 PI * * +.10000000E-01 ONE-HUNDREDTH * * -.12000000E+03 MINUS 120 * * * * NOTES: * * 1) THE BINARY BASE 10 EXPONENT IS RETURNED * * IN D7 TO FACILITATE CONVERSIONS TO * * OTHER FORMATS. * * 2) EVEN THOUGH EIGHT DIGITS ARE RETURNED,THE * * PRECISION AVAILABLE IS ONLY 7.167 DIGITS. * * ROUNDING SHOULD BE PERFORMED WHEN LESS * * THAN EIGHT DIGITS ARE ACTUALLY UTILIZED * * IN THE MANTISSA. * * 3) THE STACK IS LOWERED BY 14 BYTES BY THIS * * ROUTINE. THE RETURN ADDRESS IS REPLACED * * BY A PORTION OF THE RESULTS * * * * TIME: (8MHZ NO WAIT STATES ASSUMED) * * 330 MICROSECONDS CONVERTING THE SAMPLE * * VALUE OF 55.55 TO ASCII. * * * ****************************************************** PAGE *FFPFPA IDNT 1,1 FFP FLOAT TO ASCII * OPT PCS XREF FFP10TBL POWER OF TEN TABLE XDEF FFPFPA ENTRY POINT * STACK DEFINITION STKOLD EQU 48 PREVIOUS CALLERS STACK POINTER STKEXP EQU 46 EXPONENT STKEXPS EQU 45 EXPONENTS SIGN STKLTRE EQU 44 'E' STKMANT EQU 36 MANTISSA STKPER EQU 35 '.' STKMANS EQU 34 MANTISSA'S SIGN STKNEWRT EQU 30 NEW RETURN POSITION STKRTCC EQU 28 RETURN CONDITION CODE STKSAVE EQU 0 REGISTER SAVE AREA FFPFPA: LEA -10(SP),SP SET STACK TO NEW LOCATION MOVE.L 10(SP),-(SP) SAVE RETURN MOVE.W #0,-(SP) SAVE FOR RETURN CODE TST.B D7 TEST VALUE * MOVE.W SR,-(SP) SAVE FOR RETURN CODE (NOTE: COMMENTED OUT) MOVEM.L D2-D6/A0/A1,-(SP) SAVE REGISTERS * ADJUST FOR ZERO VALUE BNE.S FPFNOT0 BRANCH NO ZERO INPUT MOVEQ #$41,D7 SETUP PSUEDO INTEGER EXPONENT * SETUP MANTISSA'S SIGN FPFNOT0 MOVE.W #'+.',STKMANS(SP) INSERT PLUS AND DECIMAL MOVE.B D7,D6 COPY SIGN+EXPONENT BPL.S FPFPLS BRANCH IF PLUS ADDQ.B #2,STKMANS(SP) CHANGE PLUS TO MINUS * START SEARCH FOR MAGNITUDE IN BASE 10 POWER TABLE FPFPLS ADD.B D6,D6 SIGN OUT OF PICTURE MOVE.B #$80,D7 SET ROUDING FACTOR FOR SEARCH EOR.B D7,D6 CONVERT EXPONENT TO BINARY EXT.W D6 EXPONENT TO WORD ASR.W #1,D6 BACK FROM SIGN EXTRACTMENT MOVEQ #1,D3 START BASE TEN COMPUTATION LEA FFP10TBL,A0 START AT TEN TO THE ZERO CMP.W (A0),D6 COMPARE TO TABLE BLT.S FPFMIN BRANCH MINUS EXPONENT BGT.S FPFPLU BRANCH PLUS EXPONENT FPFEQE CMP.L 2(A0),D7 EQUAL SO COMPARE MANTISSA'S BCC.S FPFFND BRANCH IF INPUT GREATER OR EQUAL THAN TABLE FPFBCK ADDQ.W #6,A0 TO NEXT LOWER ENTRY IN TABLE SUBQ.W #1,D3 DECREMENT BASE 10 EXPONENT BRA.S FPFFND BRANCH POWER OF TEN FOUND * EXPONENT IS HIGHER THAN TABLE FPFPLU LEA -6(A0),A0 TO NEXT HIGHER ENTRY ADDQ.W #1,D3 INCREMENT POWER OF TEN CMP.W (A0),D6 TEST NEW MAGNITUDE BGT.S FPFPLU LOOP IF STILL GREATER BEQ.S FPFEQE BRANCH EQUAL EXPONENT BRA.S FPFBCK BACK TO LOWER AND FOUND * EXPONENT IS LOWER THAN TABLE FPFMIN LEA 6(A0),A0 TO NEXT LOWER ENTRY SUBQ.W #1,D3 DECREMENT POWER OF TEN Y ONE CMP.W (A0),D6 TEST NEW MAGNITUDE BLT.S FPFMIN LOOP IF STILL LESS THAN BEQ.S FPFEQE BRANCH EQUAL EXPONENT * CONVERT THE EXPONENT TO ASCII FPFFND MOVE.L #'E+00',STKLTRE(SP) SETUP EXPONENT PATTERN MOVE.W D3,D2 ? EXPONENT POSITIVE BPL.S FPFPEX BRANCH IF SO NEG.W D2 ABSOLUTIZE ADDQ.B #2,STKEXPS(SP) TURN TO MINUS SIGN FPFPEX CMP.W #10,D2 ? TEN OR GREATER BCS.S FPFGEN BRANCH IF NOT ADDQ.B #1,STKEXP(SP) CHANGE ZERO TO ONE SUB.W #10,D2 ADJUST TO DECIMAL FPFGEN OR.B D2,STKEXP+1(SP) FILL IN LOW DIGIT * GENERATE THE MANTISSA IN ASCII A0->TABLE D7=BINARY MANTISSA * D5 - MANTISSA FROM TABLE D6.W = BINARY EXPONENT * D4 - SHIFT AND DIGIT BUILDER D2 = DBRA MANTISSA DIGIT COUNT * A1->MANTISSA STACK POSITION MOVEQ #7,D2 COUNT FOR EIGHT DIGITS LEA STKMANT(SP),A1 POINT TO MANTISSA START TST.L D7 ? ZERO TO CONVERT BPL.S FPFZRO BRANCH IF SO TO NOT ROUND TST.B 5(A0) ? 24 BIT PRECISE IN TABLE BNE.S FPFNXI BRANCH IF NO TRAILING ZEROES FPFZRO CLR.B D7 CLEAR ADJUSTMENT FOR .5 LSB PRECISION FPFNXI MOVE.W D6,D4 COPY BINARY EXPONENT SUB.W (A0)+,D4 FIND NORMALIZATION FACTOR MOVE.L (A0)+,D5 LOAD MANTISSA FROM TABLE LSR.L D4,D5 ADJUST TO SAME EXPONENT MOVEQ #9,D4 START AT NINE AND COUNT DOWN FPFINC SUB.L D5,D7 SUBTRACT FOR ANOTHER COUNT DBCS D4,FPFINC DECREMENT AND BRANCH IF OVER BCS.S FPFNIM BRANCH NO IMPRECISION CLR.B D4 CORRECT RARE UNDERFLOW DUE TO TABLE IMPRECISION FPFNIM ADD.L D5,D7 MAKE UP FOR OVER SUBTRACTION SUB.B #9,D4 CORRECT VALUE NEG.B D4 TO BETWEEN 0 AND 9 BINARY OR.B #'0',D4 CONVERT TO ASCII MOVE.B D4,(A1)+ INSERT INTO ASCII MANTISSA PATTERN DBF D2,FPFNXI BRANCH IF MORE DIGITS TO GO * RETURN WITH BASE TEN EXPONENT BINARY IN D7 MOVE.W D3,D7 TO D7 EXT.L D7 TO FULL WORD MOVEM.L (SP)+,D2-D6/A0/A1 RESTORE REGISTERS * RTR RETURN WITH PROPER CONDITION CODE ADDQ.L #2,SP RTS END