80-Bus News

  

May-June 1984, Volume 3, Issue 3











Page 24 of 51











Dis-assembly of NASCOM ROM BASIC Ver 4.7                PAGE    92

FBEC 77         RESEED: LD      (HL),A          ; Re-seed random numbers
FBED 2B                 DEC     HL
FBEE 77                 LD      (HL),A
FBEF 2B                 DEC     HL
FBF0 77                 LD      (HL),A
FBF1 C3C7FB             JP      RND1            ; Return RND seed

FBF4 68B14668   RNDTAB: DEFB    068H,0B1H,046H,068H     ; Table used by RND
FBF8 99E99269           DEFB    099H,0E9H,092H,069H
FBFC 10D17568           DEFB    010H,0D1H,075H,068H

FC00 214AFC     COS:    LD      HL,HALFPI       ; Point to PI/2
FC03 CDBEF5             CALL    ADDPHL          ; Add it to PPREG
FC06 CD44F8     SIN:    CALL    STAKFP          ; Put angle on stack
FC09 014983             LD      BC,8349H        ; BCDE = 2 PI
FC0C 11DB0F             LD      DE,0FDBH
FC0F CD54F8             CALL    FPBCDE          ; Move 2 PI to FPREG
FC12 C1                 POP     BC              ; Restore angle
FC13 D1                 POP     DE
FC14 CD69F7             CALL    DVBCDE          ; Divide angle by 2 PI
FC17 CD44F8             CALL    STAKFP          ; Put it on stack
FC1A CDE6F8             CALL    INT             ; Get INT of result
FC1D C1                 POP     BC              ; Restore number
FC1E D1                 POP     DE
FC1F CDCAF5             CALL    SUBCDE          ; Make it 0 <= value < 1
FC22 214EFC             LD      HL,QUARTR       ; Point to 0.25
FC25 CDC4F5             CALL    SUBPHL          ; Subtract value from 0.25
FC28 CD13F8             CALL    TSTSGN          ; Test sign of value
FC2B 37                 SCF                     ; Flag positive
FC2C F236FC             JP      P,SIN1          ; Positive - Ok
FC2F CDBBF5             CALL    ROUND           ; Add 0.5 to value
FC32 CD13F8             CALL    TSTSGN          ; Test sign of value
FC35 B7                 OR      A               ; Flag negative
FC36 F5         SIN1:   PUSH    AF              ; Save sign
FC37 F43CF8             CALL    P,INVSGN        ; Negate value if positive
FC3A 214EFC             LD      HL,QUARTR       ; Point to 0.25
FC3D CDBEF5             CALL    ADDPHL          ; Add 0.25 to value
FC40 F1                 POP     AF              ; Restore sign
FC41 D43CF8             CALL    NC,INVSGN       ; Negative - Make positive
FC44 2152FC             LD      HL,SINTAB       ; Coefficient table
FC47 C35BFB             JP      SUMSER          ; Evaluate sum of series

FC4A DB0F4981   HALFPI: DEFB    0DBH,00FH,049H,081H     ; 1.5708 (PI/2)

FC4E 0000007F   QUARTR: DEFB    000H,000H,000H,07FH     ; 0.25

FC52 05         SINTAB: DEFB    5                       ; Table used by SIN
FC53 BAD71E86           DEFB    0BAH,0D7H,01EH,086H     ; 39.711
FC57 64269987           DEFB    064H,026H,099H,087H     ;-76.575
FC5B 58342387           DEFB    058H,034H,023H,087H     ; 81.602
FC5F E05DA586           DEFB    0E0H,05DH,0A5H,086H     ;-41.342
FC63 DA0F4983           DEFB    0DAH,00FH,049H,083H     ;  6.2832

Dis-assembly of NASCOM ROM BASIC Ver 4.7                PAGE    93

FC67 CD44F8     TAN:    CALL    STAKFP          ; Put angle on stack
FC6A CD06FC             CALL    SIN             ; Get SIN of angle
FC6D C1                 POP     BC              ; Restore angle
FC6E E1                 POP     HL
FC6F CD44F8             CALL    STAKFP          ; Save SIN of angle
FC72 EB                 EX      DE,HL           ; BCDE = Angle
FC73 CD54F8             CALL    FPBCDE          ; Angle to FPREG
FC76 CD00FC             CALL    COS             ; Get COS of angle
FC79 C367F7             JP      DIV             ; TAN = SIN / COS

FC7C CD13F8     ATN:    CALL    TSTSGN          ; Test sign of value
FC7F FCA7FA             CALL    M,NEGAFT        ; Negate result after if -ve
FC82 FC3CF8             CALL    M,INVSGN        ; Negate value if -ve
FC85 3AE710             LD      A,(FPEXP)       ; Get exponent
FC88 FE81               CP      81H             ; Number less than 1?
FC8A DA99FC             JP      C,ATN1          ; Yes - Get arc tangnt
FC8D 010081             LD      BC,8100H        ; BCDE = 1
FC90 51                 LD      D,C
FC91 59                 LD      E,C
FC92 CD69F7             CALL    DVBCDE          ; Get reciprocal of number
FC95 21C4F5             LD      HL,SUBPHL       ; Sub angle from PI/2
FC98 E5                 PUSH    HL              ; Save for angle > 1
FC99 21A3FC     ATN1:   LD      HL,ATNTAB       ; Coefficient table
FC9C CD5BFB             CALL    SUMSER          ; Evaluate sum of series
FC9F 214AFC             LD      HL,HALFPI       ; PI/2 - angle in case > 1
FCA2 C9                 RET                     ; Number > 1 - Sub from PI/2

FCA3 09         ATNTAB: DEFB    9                       ; Table used by ATN
FCA4 4AD73B78           DEFB    04AH,0D7H,03BH,078H     ; 1/17
FCA8 026E847B           DEFB    002H,06EH,084H,07BH     ;-1/15
FCAC FEC12F7C           DEFB    0FEH,0C1H,02FH,07CH     ; 1/13
FCB0 74319A7D           DEFB    074H,031H,09AH,07DH     ;-1/11
FCB4 843D5A7D           DEFB    084H,03DH,05AH,07DH     ; 1/9
FCB8 C87F917E           DEFB    0C8H,07FH,091H,07EH     ;-1/7
FCBC E4BB4C7E           DEFB    0E4H,0BBH,04CH,07EH     ; 1/5
FCC0 6CAAAA7F           DEFB    06CH,0AAH,0AAH,07FH     ;-1/3
FCC4 00000081           DEFB    000H,000H,000H,081H     ; 1/1


This is an OCR’d version of the scanned page and likely contains recognition errors.











Page 24 of 51