0100 ; 192K RAMDISK CONTROLLER FOR 256K ATARI 800XL (version 2)›0110 ; by Claus Buchholz, Oct., 1985›0120 ;›0130 ; OPTIONS: Drive numbers and density›0140 ; Note: If DENSITY=DOUBLE make DRIVEB=DRIVEA !›0150 ;›0160 DRIVEA=3›0170 DRIVEB=4›0180 DENSITY=SINGLE›0190 ;›0200 ; Equates›0210 ;›0220 SINGLE=$80 Sector lengths›0230 DOUBLE=$00›0240 DDEVIC=$300 SIO Device Control Block›0250 DUNIT=$301›0260 DCOMND=$302›0270 DSTATS=$303›0280 DBUFLO=$304›0290 DBYTLO=$308›0300 DAUX1=$30A›0310 DOSINI=$0C Access to RESET initialization›0320 CHKSUM=$31 Temporary checksum›0330 BUFRLO=$32 Temporary pointer to user's buffer›0340 ZTEMP=$34 Temporary miscellaneous use›0350 ZTEM2=$38 Temporary miscellaneous use›0360 STACKP=$318 Stack pointer save›0370 PORTB=$D301 PIA port B - memory control register›0380 ;›0390 ; Load-time code - Copy OS into RAM›0400 ;›0410  *=$3800›0420 GO›0430  LDA PORTB Enable Bank #3›0440  AND #$83›0450  ORA #$0C›0460  STA PORTB›0470  LDA #$C0 Zero page pointer›0480  STA $CC›0490  LDA #$40›0500  STA $CE›0510  LDA #0›0520  STA $CB›0530  STA $CD›0540  TAY›0550 LOOP›0560  LDA ($CB),Y Copy OS›0570  STA ($CD),Y›0580  INY›0590  BNE LOOP›0600  LDX $CC›0610  CPX #$CB Skip pages $CC to $D7›0620  BNE NXPG›0630  LDX #$57›0640  STX $CE›0650  LDX #$D7›0660 NXPG›0670  INC $CE›0680  INX›0690  STX $CC›0700  BNE LOOP›0710  LDA PORTB›0720  ORA #$7C Disable bank›0730  AND #$FE Enable RAM OS›0740  STA PORTB›0750  RTS  Continue load›0760  *=$2E2›0770  .WORD GO Execute preliminary load-time code›0780 ;›0790 ; Ramdisk controller code›0800 ;›0810  *=$CC00 Permanent code - in place of alt. char. set›0820 HOOK›0830  CLC  Hook into all SIO calls›0840  LDA DDEVIC›0850  ADC DUNIT›0860  LDY #$00 DRIVEA offset›0870  CMP #$31+DRIVEA Right drive number?›0880  BEQ HOOKED›0890  LDY #$80 DRIVEB offset›0900  CMP #$31+DRIVEB›0910  BEQ HOOKED›0920 OLDVEC=*+1›0930  JMP * If not, go to SIO›0940 HOOKED›0950  TSX  If so, intercept›0960  STX STACKP Save stack pointer›0970  STY ZTEM2 Store offset›0980  LDA DCOMND Examine command›0990  CMP #'! Format?›1000  BNE NOFMT›1010  JMP FORMAT›1020 NOFMT›1030  CMP #'P Put sector?›1040  BNE NOPUT›1050  JMP PUTSEC›1060 NOPUT›1070  CMP #'R Read sector?›1080  BNE NOGET›1090  JMP GETSEC›1100 NOGET›1110  CMP #'S Read status?›1120  BNE NOSTT›1130  JMP STATUS›1140 NOSTT›1150  CMP #'W Write sector?›1160  BNE NAKRET›1170  JMP PUTSEC›1180 ;›1190 ; Returns - Restore stack pointer, report error status and return›1200 ;›1210 NAKRET›1220  LDX STACKP›1230  TXS›1240  LDY #139 NAK error for improper command›1250  STY DSTATS›1260  RTS›1270 ERRRET›1280  LDX STACKP›1290  TXS›1300  LDY #144 Bad sector error›1310  STY DSTATS›1320  RTS›1330 SUCRET›1340  LDX STACKP›1350  TXS›1360  LDY #1 No error›1370  STY DSTATS›1380  RTS›1390 ;›1400 ; Subroutine - Set pointer to user buffer›1410 ;›1420 SETBUF›1430  LDA DBUFLO Move from DCB to zero page›1440  STA BUFRLO›1450  LDA DBUFLO+1›1460  STA BUFRLO+1›1470  RTS›1480 ;›1490 ; Subroutine - Prepare to access sector of ramdisk›1500 ;›1510 SETSEC›1520  LDA #DENSITY›1530  STA SECLEN Set sector length›1540  LDA DAUX1+1 Check sector #›1550  BNE NOTZ›1560  LDA DAUX1›1570  BEQ OUTRG Sector 0 invalid›1580  CMP #4›1590  BCS INRNG›1600  LDA #$80 Sectors 1-3 always 128 bytes long›1610  STA SECLEN›1620  BNE INRNG›1630 OUTRG›1640  JMP NAKRET Sector # out of range›1650 NOTZ›1660  CMP #2 Check for sector # > $2D0›1670  BCC INRNG›1680  BNE OUTRG›1690  LDA #$D0›1700  CMP DAUX1›1710  BCC OUTRG›1720 INRNG›1730  LDA DAUX1 Sector # valid›1740  STA ZTEMP›1750  LDA DAUX1+1›1760  ASL ZTEMP›1770  ROL A Divide # by 64 - Result is bank #, remainder is page #›1780  ASL ZTEMP›1790  ROL A›1800  ADC #4 Bank #›1810  TAX›1820  LDA ZTEMP›1830  LSR A›1840  LSR A›1850  ADC #$40 Remainder+64›1860 ;›1870 ; Subroutine - Prepare to switch banks:›1880 ; X is bank #, A is page #›1890 ;›1900 SETBNK›1910  STA ZTEM2+1 Save page #›1920  LDA PORTB›1930  STA PBN Normal bank›1940  AND #$83›1950  STA PB Bank 0›1960  TXA›1970  ASL A›1980  ASL A›1990  PHA›2000  AND #$0C›2010  ORA PB›2020  STA PB›2030  PLA›2040  ASL A›2050  AND #$60›2060  ORA PB›2070  STA PB Bank X›2080  LDA $FFFA NMI vector›2090  STA ZTEMP›2100  LDA $FFFB›2110  STA ZTEMP+1›2120  LDY #0›2130  LDA #$40 RTI opcode›2140  SEI  Disable IRQ›2150  STA (ZTEMP),Y Place RTI in NMI routine - disables NMI›2160  RTS  Leave 0 in Y, bank # in X›2170 ;›2180 ; Format routine›2190 ;›2200 FORMAT›2210  LDX #4 Clear banks 4 to F›2220 CLOOP1›2230  LDA #$40›2240  JSR SETBNK Prepare for switch›2250  LDA PB›2260  STA PORTB Switch bank in›2270  TYA›2280 CLOOP2›2290  STA (ZTEM2),Y Zero entire sector›2300  INY›2310  CPY SECLEN›2320  BNE CLOOP2›2330  TAY›2340  INC ZTEM2+1 Next page›2350  BPL CLOOP2›2360  LDA PBN›2370  STA PORTB Switch bank out›2380  LDA NMI›2390  STA (ZTEMP),Y Enable interrupts›2400  CLI›2410  INX  Next bank›2420  CPX #$10 Done?›2430  BCC CLOOP1›2440  JSR SETBUF›2450  LDA #$FF Return a sector with 2 $FFs and the rest 0s›2460  LDY #0›2470 FLOOP›2480  CPY #2›2490  BNE NOTFF›2500  LDA #0›2510 NOTFF›2520  STA (BUFRLO),Y›2530  INY›2540  CPY SECLEN›2550  BNE FLOOP›2560  JMP SUCRET Done›2570 ;›2580 ; Write sector routine›2590 ;›2600 PUTSEC›2610  JSR SETBUF›2620  LDA #0›2630  STA CHKSUM Zero checksum›2640  JSR SETSEC Point to ramdisk sector›2650 PLOOP›2660  LDA (BUFRLO),Y Get byte from user's buffer›2670  LDX PB›2680  STX PORTB Switch bank›2690  STA (ZTEM2),Y Put byte into ramdisk›2700  LDX PBN›2710  STX PORTB Normal bank›2720  CLC›2730  ADC CHKSUM Add byte to checksum›2740  STA CHKSUM›2750  INY  Next byte›2760  CPY SECLEN Proper sector length›2770  BNE PLOOP›2780  LDX #$F Bank F holds checksum table›2790  LDA DAUX1›2800  ASL A›2810  LDA DAUX1+1›2820  ROL A›2830  ORA #$60 Sector # indexes checksum table›2840  JSR SETBNK›2850  LDA DAUX1›2860  AND #$7F›2870  TAY›2880  LDA CHKSUM›2890  LDX PB›2900  STX PORTB Switch bank›2910  STA (ZTEM2),Y Store checksum›2920  LDX PBN›2930  STX PORTB Normal bank›2940  LDY #0›2950  LDA NMI›2960  STA (ZTEMP),Y Enable interrupts›2970  CLI›2980  JMP SUCRET Done›2990 ;›3000 ; Read sector routine›3010 ;›3020 GETSEC›3030  JSR SETBUF›3040  LDA #0›3050  STA CHKSUM Zero checksum›3060  JSR SETSEC›3070 GLOOP›3080  LDX PB›3090  STX PORTB Switch bank›3100  LDA (ZTEM2),Y Get byte from ramdisk›3110  LDX PBN›3120  STX PORTB Normal bank›3130  STA (BUFRLO),Y Put byte into user's buffer›3140  CLC›3150  ADC CHKSUM Add to checksum›3160  STA CHKSUM›3170  INY  Next byte›3180  CPY SECLEN Proper sector length›3190  BNE GLOOP›3200  LDX #$F Bank F for checksum table›3210  LDA DAUX1›3220  ASL A›3230  LDA DAUX1+1›3240  ROL A›3250  ORA #$60›3260  JSR SETBNK›3270  LDA DAUX1›3280  AND #$7F›3290  TAY›3300  LDX PB›3310  STX PORTB Switch bank›3320  LDA (ZTEM2),Y Get original checksum›3330  LDX PBN›3340  STX PORTB Normal bank›3350  TAX›3360  LDY #0›3370  LDA NMI›3380  STA (ZTEMP),Y Enable interrupts›3390  CLI›3400  CPX CHKSUM Compare checksums›3410  BEQ GCSOK›3420  JMP ERRRET If different, bad sector›3430 GCSOK›3440  JMP SUCRET If same, done›3450 ;›3460 ; Read status routine›3470 ;›3480 STATUS›3490  JSR SETBUF›3500  LDY #3 Return 4 bytes›3510  LDA #0 All 0s›3520 SLOOP›3530  STA (BUFRLO),Y›3540  DEY›3550  BPL SLOOP›3560  CMP #DENSITY›3570  BNE SDONE›3580  LDA #$20›3590  INY›3600  STA (BUFRLO),Y First byte tells density of drive›3610 SDONE›3620  JMP SUCRET Done›3630 ;›3640 ; Variable storage area›3650 ;›3660 PB *=*+1 Value of memory control register for selected bank›3670 PBN *=*+1 Value of memory control register for normal bank›3680 NMI *=*+1 First opcode in NMI routine - Used to restore NMI›3690 SECLEN *=*+1 Length of current sector›3700 ;›3710 ; RESET initialization routine›3720 ;›3730  *=$100 Hidden (hopefully)›3740 NEWINI›3750  DEC PORTB Enable RAM OS›3760 OLDINI=*+1›3770  JSR * Call original DOSINI routine›3780 MODINI›3790  LDA #NEWINI&$FF Set hook for next RESET›3800  STA DOSINI›3810  LDA #NEWINI/$100›3820  STA DOSINI+1›3830  RTS›3840 ;›3850 ; Load-time code - Install ramdisk›3860 ;›3870  *=$3800›3880 DO›3890  LDA $E45A Save original SIO vector›3900  STA OLDVEC›3910  LDA $E45B›3920  STA OLDVEC+1›3930  LDA #HOOK&$FF Install new SIO vector›3940  STA $E45A›3950  LDA #HOOK/$100›3960  STA $E45B›3970  LDA $FFFA Save first opcode in NMI routine›3980  STA $CB›3990  LDA $FFFB›4000  STA $CC›4010  LDY #0›4020  LDA ($CB),Y›4030  STA NMI›4040  LDA DOSINI Save original DOSINI vector›4050  STA OLDINI›4060  LDA DOSINI+1›4070  STA OLDINI+1›4080  JSR MODINI Install new one›4090  JSR $7E0 Re-initialize FMS to show ramdisk present›4100  RTS  Done›4110  *=$2E2›4120  .WORD DO Execute final load-time code›