0100 ; 96K RAMDISK CONTROLLER FOR 256K ATARI 800XL (version 2)›0110 ; by Claus Buchholz, Oct., 1985›0120 ;›0130 ; OPTION: Drive number›0140 ;›0150 DRIVE=3›0160 ;›0170 ; Equates›0180 ;›0190 DDEVIC=$300 SIO Device Control Block›0200 DUNIT=$301›0210 DCOMND=$302›0220 DSTATS=$303›0230 DBUFLO=$304›0240 DBYTLO=$308›0250 DAUX1=$30A›0260 DOSINI=$0C Access to RESET initialization›0270 CHKSUM=$31 Temporary checksum›0280 BUFRLO=$32 Temporary pointer to user's buffer›0290 ZTEMP=$34 Temporary miscellaneous use›0300 ZTEM2=$38 Temporary miscellaneous use›0310 STACKP=$318 Stack pointer save›0320 PORTB=$D301 PIA port B - memory control register›0330 ;›0340 ; Load-time code - Copy OS into RAM›0350 ;›0360  *=$3800›0370 GO›0380  LDA PORTB Enable Bank #3›0390  AND #$83›0400  ORA #$0C›0410  STA PORTB›0420  LDA #$C0 Zero page pointer›0430  STA $CC›0440  LDA #$40›0450  STA $CE›0460  LDA #0›0470  STA $CB›0480  STA $CD›0490  TAY›0500 LOOP›0510  LDA ($CB),Y Copy OS›0520  STA ($CD),Y›0530  INY›0540  BNE LOOP›0550  LDX $CC›0560  CPX #$CB Skip pages $CC to $D7›0570  BNE NXPG›0580  LDX #$57›0590  STX $CE›0600  LDX #$D7›0610 NXPG›0620  INC $CE›0630  INX›0640  STX $CC›0650  BNE LOOP›0660  LDA PORTB›0670  ORA #$7C Disable bank›0680  AND #$FE Enable RAM OS›0690  STA PORTB›0700  RTS  Continue load›0710  *=$2E2›0720  .WORD GO Execute preliminary load-time code›0730 ;›0740 ; Ramdisk controller code›0750 ;›0760  *=$CC00 Permanent code - in place of alt. char. set›0770 HOOK›0780  CLC  Hook into all SIO calls›0790  LDA DDEVIC›0800  ADC DUNIT›0810  CMP #$31+DRIVE Right drive number?›0820  BEQ HOOKED›0830 OLDVEC=*+1›0840  JMP * If not, go to SIO›0850 HOOKED›0860  TSX  If so, intercept›0870  STX STACKP Save stack pointer›0880  LDA DCOMND Examine command›0890  CMP #'! Format?›0900  BNE NOFMT›0910  JMP FORMAT›0920 NOFMT›0930  CMP #'P Put sector?›0940  BNE NOPUT›0950  JMP PUTSEC›0960 NOPUT›0970  CMP #'R Read sector?›0980  BNE NOGET›0990  JMP GETSEC›1000 NOGET›1010  CMP #'S Read status?›1020  BNE NOSTT›1030  JMP STATUS›1040 NOSTT›1050  CMP #'W Write sector?›1060  BNE NAKRET›1070  JMP PUTSEC›1080 ;›1090 ; Returns - Restore stack pointer, report error status and return›1100 ;›1110 NAKRET›1120  LDX STACKP›1130  TXS›1140  LDY #139 NAK error for improper command›1150  STY DSTATS›1160  RTS›1170 ERRRET›1180  LDX STACKP›1190  TXS›1200  LDY #144 Bad sector error›1210  STY DSTATS›1220  RTS›1230 SUCRET›1240  LDX STACKP›1250  TXS›1260  LDY #1 No error›1270  STY DSTATS›1280  RTS›1290 ;›1300 ; Subroutine - Set pointer to user buffer›1310 ;›1320 SETBUF›1330  LDA DBUFLO Move from DCB to zero page›1340  STA BUFRLO›1350  LDA DBUFLO+1›1360  STA BUFRLO+1›1370  RTS›1380 ;›1390 ; Subroutine - Prepare to access sector of ramdisk›1400 ;›1410 SETSEC›1420  LDA DAUX1+1 Check sector #›1430  BNE NOTZ›1440  LDA DAUX1›1450  BNE INRNG Sector 0 invalid›1460 OUTRG›1470  JMP NAKRET Sector # out of range›1480 NOTZ›1490  CMP #2 Check for sector # > $2D0›1500  BCC INRNG›1510  BNE OUTRG›1520  LDA #$D0›1530  CMP DAUX1›1540  BCC OUTRG›1550 INRNG›1560  LDA DAUX1 Sector # valid›1570  ASL A›1580  LDA DAUX1+1›1590  ROL A Divide # by 128 - Result is bank #, remainder is page #›1600  ADC #4 Bank #›1610  TAX›1620  LDA DAUX1›1630  ORA #$80 Remainder+128›1640 ;›1650 ; Subroutine - Prepare to switch banks:›1660 ; X is bank #, A is 2*page #›1670 ;›1680 SETBNK›1690  LSR A›1700  STA ZTEM2+1 Save page #›1710  LDA #0›1720  ROR A›1730  STA ZTEM2›1740  LDA PORTB›1750  STA PBN Normal bank›1760  AND #$83›1770  STA PB Bank 0›1780  TXA›1790  ASL A›1800  ASL A›1810  PHA›1820  AND #$0C›1830  ORA PB›1840  STA PB›1850  PLA›1860  ASL A›1870  AND #$60›1880  ORA PB›1890  STA PB Bank X›1900  LDA $FFFA NMI vector›1910  STA ZTEMP›1920  LDA $FFFB›1930  STA ZTEMP+1›1940  LDY #0›1950  LDA #$40 RTI opcode›1960  SEI  Disable IRQ›1970  STA (ZTEMP),Y Place RTI in NMI routine - disables NMI›1980  RTS  Leave 0 in Y, bank # in X›1990 ;›2000 ; Format routine›2010 ;›2020 FORMAT›2030  LDX #4 Clear banks 4 to 9›2040 CLOOP1›2050  LDA #$80›2060  JSR SETBNK Prepare for switch›2070  LDA PB›2080  STA PORTB Switch bank in›2090  TYA›2100 CLOOP2›2110  STA (ZTEM2),Y Zero entire page›2120  INY›2130  BNE CLOOP2›2140  INC ZTEM2+1 Next page›2150  BPL CLOOP2›2160  LDA PBN›2170  STA PORTB Switch bank out›2180  LDA NMI›2190  STA (ZTEMP),Y Enable interrupts›2200  CLI›2210  INX  Next bank›2220  CPX #$A Done?›2230  BCC CLOOP1›2240  JSR SETBUF›2250  LDA #$FF Return a sector with 2 $FFs and the rest 0s›2260  LDY #0›2270 FLOOP›2280  CPY #2›2290  BNE NOTFF›2300  LDA #0›2310 NOTFF›2320  STA (BUFRLO),Y›2330  INY›2340  BPL FLOOP›2350  JMP SUCRET Done›2360 ;›2370 ; Write sector routine›2380 ;›2390 PUTSEC›2400  JSR SETBUF›2410  LDA #0›2420  STA CHKSUM Zero checksum›2430  JSR SETSEC Point to ramdisk sector›2440 PLOOP›2450  LDA (BUFRLO),Y Get byte from user's buffer›2460  LDX PB›2470  STX PORTB Switch bank›2480  STA (ZTEM2),Y Put byte into ramdisk›2490  LDX PBN›2500  STX PORTB Normal bank›2510  CLC›2520  ADC CHKSUM Add byte to checksum›2530  STA CHKSUM›2540  INY  Next byte›2550  BPL PLOOP›2560  LDX #9 Bank 9 holds checksum table›2570  LDA DAUX1+1›2580  ORA #$70 Sector # indexes checksum table›2590  ASL A›2600  JSR SETBNK›2610  LDY DAUX1›2620  LDA CHKSUM›2630  LDX PB›2640  STX PORTB Switch bank›2650  STA (ZTEM2),Y Store checksum›2660  LDX PBN›2670  STX PORTB Normal bank›2680  LDY #0›2690  LDA NMI›2700  STA (ZTEMP),Y Enable interrupts›2710  CLI›2720  JMP SUCRET Done›2730 ;›2740 ; Read sector routine›2750 ;›2760 GETSEC›2770  JSR SETBUF›2780  LDA #0›2790  STA CHKSUM Zero checksum›2800  JSR SETSEC›2810 GLOOP›2820  LDX PB›2830  STX PORTB Switch bank›2840  LDA (ZTEM2),Y Get byte from ramdisk›2850  LDX PBN›2860  STX PORTB Normal bank›2870  STA (BUFRLO),Y Put byte into user's buffer›2880  CLC›2890  ADC CHKSUM Add to checksum›2900  STA CHKSUM›2910  INY  Next byte›2920  BPL GLOOP›2930  LDX #9 Bank 9 holds checksum table›2940  LDA DAUX1+1›2950  ORA #$70 Sector # indexes checksum table›2960  ASL A›2970  JSR SETBNK›2980  LDY DAUX1›2990  LDX PB›3000  STX PORTB Switch bank›3010  LDA (ZTEM2),Y Get original checksum›3020  LDX PBN›3030  STX PORTB Normal bank›3040  TAX›3050  LDY #0›3060  LDA NMI›3070  STA (ZTEMP),Y Enable interrupts›3080  CLI›3090  CPX CHKSUM Compare checksums›3100  BEQ GCSOK›3110  JMP ERRRET If different, bad sector›3120 GCSOK›3130  JMP SUCRET If same, done›3140 ;›3150 ; Read status routine›3160 ;›3170 STATUS›3180  JSR SETBUF›3190  LDY #3 Return 4 bytes›3200  LDA #0 All 0s›3210 SLOOP›3220  STA (BUFRLO),Y›3230  DEY›3240  BPL SLOOP›3250  JMP SUCRET Done›3260 ;›3270 ; Variable storage area›3280 ;›3290 PB *=*+1 Value of memory control register for selected bank›3300 PBN *=*+1 Value of memory control register for normal bank›3310 NMI *=*+1 First opcode in NMI routine - Used to restore NMI›3320 ;›3330 ; RESET initialization routine›3340 ;›3350  *=$100 Hidden (hopefully)›3360 NEWINI›3370  DEC PORTB Enable RAM OS›3380 OLDINI=*+1›3390  JSR * Call original DOSINI routine›3400 MODINI›3410  LDA #NEWINI&$FF Set hook for next RESET›3420  STA DOSINI›3430  LDA #NEWINI/$100›3440  STA DOSINI+1›3450  RTS›3460 ;›3470 ; Load-time code - Install ramdisk›3480 ;›3490  *=$3800›3500 DO›3510  LDA $E45A Save original SIO vector›3520  STA OLDVEC›3530  LDA $E45B›3540  STA OLDVEC+1›3550  LDA #HOOK&$FF Install new SIO vector›3560  STA $E45A›3570  LDA #HOOK/$100›3580  STA $E45B›3590  LDA $FFFA Save first opcode in NMI routine›3600  STA $CB›3610  LDA $FFFB›3620  STA $CC›3630  LDY #0›3640  LDA ($CB),Y›3650  STA NMI›3660  LDA DOSINI Save original DOSINI vector›3670  STA OLDINI›3680  LDA DOSINI+1›3690  STA OLDINI+1›3700  JSR MODINI Install new one›3710  JSR $7E0 Re-initialize FMS to show ramdisk present›3720  RTS  Done›3730  *=$2E2›3740  .WORD DO Execute final load-time code›