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Boot Rom listing.. for those interested
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John Crane
Aug 7, 2012, 7:01:24 PM8/7/12
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;
; North-Star MDS-A disk boot rom disassembly
;
E900 31 14 21 LXI S,$2114 ; Set stack
E903 06 0A MVI B,$0A ; Set retry count (10)
E905 C5 PUSH B ; [2112] = Retry count
E906 3E 59 MVI A,$59 ; Get flag value
E908 32 00 20 STA $2000 ; Set flag1
E90B 32 03 20 STA $2003 ; Set last drive (invalid)
E90E 01 01 00 LXI B,$0001 ; Drive 1
E911 79 MOV A,C ; A = 01 (Track)
E912 16 04 MVI D,$04 ; Sector 4
E914 59 MOV E,C ; E = 01 (Drive)
E915 21 00 20 LXI H,$2000 ; Load address
E918 CD 1E E9 CALL $E91E ; [2110] = e91b
E91B C3 98 E9 JMP $E998 ; And launch
; Disk access subroutine
; A=#blks B=track C=drive D=Sector E=01Read/00Write/03Verify* HL=RamAddr
; [*: only Read is native, Write/Verify jump back to NorthStar DOS]
E91E F5 PUSH PSW ; [210E] = 01xx - Save #blocks
E91F E5 PUSH H ; [210C] = 2000 - Save RAM addr
E920 D5 PUSH D ; [210A] = 0401 - Save sector/func
E921 C5 PUSH B ; [2108] = 0001 - Save track/drive
E922 06 EB MVI B,$EB ; High access
E924 CD E0 E9 CALL $E9E0 ; Motors ON and select drive [C]
E927 21 FF 34 LXI H,$34FF ; Offset to 2000
E92A 09 DAD B ; HL = 2000 (RAM address)
E92B 7E MOV A,M ; Get flag
E92C EE 59 XRI $59 ; Has it changed? (First call)
E92E E5 PUSH H ; s[2106] = 2000 (Save RAM addr)
E92F CC 64 E9 CZ $E964 ; Step to track 0
E932 E1 POP H ; <[2106] Ram address
E933 F1 POP PSW ; <[2108] Track # (from BC)
E934 CD 64 E9 CALL $E964 ; Step to track
E937 C1 POP B ; <[210A] Sector/function
E938 CD CE E9 CALL $E9CE ; Wait one sector time
E93B 3A 30 EB LDA $EB30 ; Read B status
E93E E6 0F ANI $0F ; Save only sector number
E940 B8 CMP B ; Are we at sector
E941 C2 38 E9 JNZ $E938 ; No, wait for it
E944 E1 POP H ; <[210C] Ram address
E945 0D DCR C ; Test function
E946 FA 0A 20 JM $200A ; 00=Write
E949 C2 07 20 JNZ $2007 ; !01=Verify
; Read block of data from drive
E94C 06 8C MVI B,$8C ; Timeout count
E94E 11 50 EB LXI D,$EB50 ; Read data
E951 0E 00 MVI C,$00 ; Read 256 bytes
E953 3A 10 EB LDA $EB10 ; Get status
E956 E6 04 ANI $04 ; Wait for Body
E958 C2 AE E9 JNZ $E9AE ; Body - ready for data
E95B 05 DCR B ; Reduce timeout
E95C C2 53 E9 JNZ $E953 ; Wait for it
E95F 3E 01 MVI A,$01 ; Report TIMEOUT error
E961 C3 AB E9 JMP $E9AB ; And exit
;
; Step to track [A]
; On exit, D=0, C=0, A=1 if at track0
;
E964 57 MOV D,A ; Save track ID
E965 96 SUB M ; Compute difference
E966 72 MOV M,D ; Save new track
E967 C8 RZ ; Already there
E968 21 1D EB LXI H,$EB1D ; Assume Step IN
E96B 4F MOV C,A ; Set # tracks
E96C F2 7B E9 JP $E97B ; Assumption correct
E96F 2F CMA ; Adjust to -number
E970 3C INR A ; of track
E971 4F MOV C,A ; And set new value
E972 3A 10 EB LDA $EB10 ; Read status
E975 E6 01 ANI $01 ; At track 0
E977 C0 RNZ ; Can't step further
E978 21 1C EB LXI H,$EB1C ; Set Step OUT
E97B 7E MOV A,M ; Set STEP high
E97C 3A 09 EB LDA $EB09 ; NOP, M0=1
E97F E3 XTHL ; Delay
E980 E3 XTHL ; Delay
E981 3A 08 EB LDA $EB08 ; Drop M0
E984 16 02 MVI D,$02 ; Wait 2 sector times
E986 CD D0 E9 CALL $E9D0 ; Wait
E989 3A 10 EB LDA $EB10 ; Read status
E98C E6 01 ANI $01 ; At track 0
E98E CA 93 E9 JZ $E993 ; No, don't stop
E991 0E 01 MVI C,$01 ; Abort step
E993 0D DCR C ; Reduce count
E994 C2 7C E9 JNZ $E97C ; Do them all
E997 C9 RET
; Read complete - launch BOOT if no errors
E998 C1 POP B ; Restore retry count
E999 CA 04 20 JZ $2004 ; OK, launch OS
E99C 05 DCR B ; Reduce count
E99D C2 05 E9 JNZ $E905 ; Try again...
E9A0 C3 A0 E9 JMP $E9A0 ; Give up (Hang)
E9A3 00 NOP
E9A4 00 NOP
E9A5 00 NOP
E9A6 00 NOP
E9A7 00 NOP
E9A8 00 NOP
E9A9 00 NOP
E9AA 00 NOP
; Report failure - cleam stack & set Z/!Z
E9AB C1 POP B
E9AC B7 ORA A
E9AD C9 RET
;
; Read data sector from disk
;
E9AE 41 MOV B,C ; Zero checkval
E9AF 1A LDAX D ; Read data byte
E9B0 77 MOV M,A ; Write to RAM
E9B1 A8 XRA B ; Compute
E9B2 07 RLC ; Check
E9B3 47 MOV B,A ; Resave check
E9B4 23 INX H ; Next RAM address
E9B5 0D DCR C ; Reduce count
E9B6 C2 AF E9 JNZ $E9AF ; Read them all
E9B9 1A LDAX D ; Read check value
E9BA A8 XRA B ; Does it match?
E9BB CA C4 E9 JZ $E9C4 ; Yes, it's OK
E9BE 78 MOV A,B ; ??
E9BF 3E 02 MVI A,$02 ; Report CRC error
E9C1 C3 AB E9 JMP $E9AB ; And exit
E9C4 F1 POP PSW ; [210E] Sector count
E9C5 3D DCR A ; Reduce count
E9C6 C8 RZ ; All done
E9C7 F5 PUSH PSW ; Resave count
E9C8 CD CE E9 CALL $E9CE ; Wait 1 sector
E9CB C3 4C E9 JMP $E94C ; And read next
;
; Wait one sector time
;
E9CE 16 01 MVI D,$01 ; Single sector time
;
; Wait [D] sector times
;
E9D0 3A 14 EB LDA $EB14 ; Reset sector flag
E9D3 3A 90 EB LDA $EB90 ; Read status
E9D6 E6 80 ANI $80 ; Sector pulse?
E9D8 CA D3 E9 JZ $E9D3 ; Wait for it
E9DB 15 DCR D ; Reduce count
E9DC C8 RZ ; Finished
E9DD C3 D0 E9 JMP $E9D0 ; Keep waiting
;
; Turn drive motors ON [C]=Drive
;
E9E0 3A 90 EB LDA $EB90 ; Motors ON & statusA
E9E3 E6 10 ANI $10 ; Already ON?
E9E5 C2 F0 E9 JNZ $E9F0 ; Yes, short wait
E9E8 16 32 MVI D,$32 ; Wait 32 sector times
E9EA CD D0 E9 CALL $E9D0 ; Wait
E9ED C3 F5 E9 JMP $E9F5 ; And select drove
E9F0 3A 03 20 LDA $2003 ; Get last drive
E9F3 B9 CMP C ; Same drive?
E9F4 C8 RZ ; Yes, no need to wait
E9F5 0A LDAX B ; Select new drive
E9F6 79 MOV A,C ; Get drive ID
E9F7 32 03 20 STA $2003 ; Set new flag
E9FA 16 0D MVI D,$0D ; Wait 13 sector tiems
E9FC C3 D0 E9 JMP $E9D0 ; Wait & return
E9FF 00 NOP
--
-John
email: john_crane_Z@yahoodotcom
where: Z=12*5-1
; North-Star MDS-A disk boot rom disassembly
;
E900 31 14 21 LXI S,$2114 ; Set stack
E903 06 0A MVI B,$0A ; Set retry count (10)
E905 C5 PUSH B ; [2112] = Retry count
E906 3E 59 MVI A,$59 ; Get flag value
E908 32 00 20 STA $2000 ; Set flag1
E90B 32 03 20 STA $2003 ; Set last drive (invalid)
E90E 01 01 00 LXI B,$0001 ; Drive 1
E911 79 MOV A,C ; A = 01 (Track)
E912 16 04 MVI D,$04 ; Sector 4
E914 59 MOV E,C ; E = 01 (Drive)
E915 21 00 20 LXI H,$2000 ; Load address
E918 CD 1E E9 CALL $E91E ; [2110] = e91b
E91B C3 98 E9 JMP $E998 ; And launch
; Disk access subroutine
; A=#blks B=track C=drive D=Sector E=01Read/00Write/03Verify* HL=RamAddr
; [*: only Read is native, Write/Verify jump back to NorthStar DOS]
E91E F5 PUSH PSW ; [210E] = 01xx - Save #blocks
E91F E5 PUSH H ; [210C] = 2000 - Save RAM addr
E920 D5 PUSH D ; [210A] = 0401 - Save sector/func
E921 C5 PUSH B ; [2108] = 0001 - Save track/drive
E922 06 EB MVI B,$EB ; High access
E924 CD E0 E9 CALL $E9E0 ; Motors ON and select drive [C]
E927 21 FF 34 LXI H,$34FF ; Offset to 2000
E92A 09 DAD B ; HL = 2000 (RAM address)
E92B 7E MOV A,M ; Get flag
E92C EE 59 XRI $59 ; Has it changed? (First call)
E92E E5 PUSH H ; s[2106] = 2000 (Save RAM addr)
E92F CC 64 E9 CZ $E964 ; Step to track 0
E932 E1 POP H ; <[2106] Ram address
E933 F1 POP PSW ; <[2108] Track # (from BC)
E934 CD 64 E9 CALL $E964 ; Step to track
E937 C1 POP B ; <[210A] Sector/function
E938 CD CE E9 CALL $E9CE ; Wait one sector time
E93B 3A 30 EB LDA $EB30 ; Read B status
E93E E6 0F ANI $0F ; Save only sector number
E940 B8 CMP B ; Are we at sector
E941 C2 38 E9 JNZ $E938 ; No, wait for it
E944 E1 POP H ; <[210C] Ram address
E945 0D DCR C ; Test function
E946 FA 0A 20 JM $200A ; 00=Write
E949 C2 07 20 JNZ $2007 ; !01=Verify
; Read block of data from drive
E94C 06 8C MVI B,$8C ; Timeout count
E94E 11 50 EB LXI D,$EB50 ; Read data
E951 0E 00 MVI C,$00 ; Read 256 bytes
E953 3A 10 EB LDA $EB10 ; Get status
E956 E6 04 ANI $04 ; Wait for Body
E958 C2 AE E9 JNZ $E9AE ; Body - ready for data
E95B 05 DCR B ; Reduce timeout
E95C C2 53 E9 JNZ $E953 ; Wait for it
E95F 3E 01 MVI A,$01 ; Report TIMEOUT error
E961 C3 AB E9 JMP $E9AB ; And exit
;
; Step to track [A]
; On exit, D=0, C=0, A=1 if at track0
;
E964 57 MOV D,A ; Save track ID
E965 96 SUB M ; Compute difference
E966 72 MOV M,D ; Save new track
E967 C8 RZ ; Already there
E968 21 1D EB LXI H,$EB1D ; Assume Step IN
E96B 4F MOV C,A ; Set # tracks
E96C F2 7B E9 JP $E97B ; Assumption correct
E96F 2F CMA ; Adjust to -number
E970 3C INR A ; of track
E971 4F MOV C,A ; And set new value
E972 3A 10 EB LDA $EB10 ; Read status
E975 E6 01 ANI $01 ; At track 0
E977 C0 RNZ ; Can't step further
E978 21 1C EB LXI H,$EB1C ; Set Step OUT
E97B 7E MOV A,M ; Set STEP high
E97C 3A 09 EB LDA $EB09 ; NOP, M0=1
E97F E3 XTHL ; Delay
E980 E3 XTHL ; Delay
E981 3A 08 EB LDA $EB08 ; Drop M0
E984 16 02 MVI D,$02 ; Wait 2 sector times
E986 CD D0 E9 CALL $E9D0 ; Wait
E989 3A 10 EB LDA $EB10 ; Read status
E98C E6 01 ANI $01 ; At track 0
E98E CA 93 E9 JZ $E993 ; No, don't stop
E991 0E 01 MVI C,$01 ; Abort step
E993 0D DCR C ; Reduce count
E994 C2 7C E9 JNZ $E97C ; Do them all
E997 C9 RET
; Read complete - launch BOOT if no errors
E998 C1 POP B ; Restore retry count
E999 CA 04 20 JZ $2004 ; OK, launch OS
E99C 05 DCR B ; Reduce count
E99D C2 05 E9 JNZ $E905 ; Try again...
E9A0 C3 A0 E9 JMP $E9A0 ; Give up (Hang)
E9A3 00 NOP
E9A4 00 NOP
E9A5 00 NOP
E9A6 00 NOP
E9A7 00 NOP
E9A8 00 NOP
E9A9 00 NOP
E9AA 00 NOP
; Report failure - cleam stack & set Z/!Z
E9AB C1 POP B
E9AC B7 ORA A
E9AD C9 RET
;
; Read data sector from disk
;
E9AE 41 MOV B,C ; Zero checkval
E9AF 1A LDAX D ; Read data byte
E9B0 77 MOV M,A ; Write to RAM
E9B1 A8 XRA B ; Compute
E9B2 07 RLC ; Check
E9B3 47 MOV B,A ; Resave check
E9B4 23 INX H ; Next RAM address
E9B5 0D DCR C ; Reduce count
E9B6 C2 AF E9 JNZ $E9AF ; Read them all
E9B9 1A LDAX D ; Read check value
E9BA A8 XRA B ; Does it match?
E9BB CA C4 E9 JZ $E9C4 ; Yes, it's OK
E9BE 78 MOV A,B ; ??
E9BF 3E 02 MVI A,$02 ; Report CRC error
E9C1 C3 AB E9 JMP $E9AB ; And exit
E9C4 F1 POP PSW ; [210E] Sector count
E9C5 3D DCR A ; Reduce count
E9C6 C8 RZ ; All done
E9C7 F5 PUSH PSW ; Resave count
E9C8 CD CE E9 CALL $E9CE ; Wait 1 sector
E9CB C3 4C E9 JMP $E94C ; And read next
;
; Wait one sector time
;
E9CE 16 01 MVI D,$01 ; Single sector time
;
; Wait [D] sector times
;
E9D0 3A 14 EB LDA $EB14 ; Reset sector flag
E9D3 3A 90 EB LDA $EB90 ; Read status
E9D6 E6 80 ANI $80 ; Sector pulse?
E9D8 CA D3 E9 JZ $E9D3 ; Wait for it
E9DB 15 DCR D ; Reduce count
E9DC C8 RZ ; Finished
E9DD C3 D0 E9 JMP $E9D0 ; Keep waiting
;
; Turn drive motors ON [C]=Drive
;
E9E0 3A 90 EB LDA $EB90 ; Motors ON & statusA
E9E3 E6 10 ANI $10 ; Already ON?
E9E5 C2 F0 E9 JNZ $E9F0 ; Yes, short wait
E9E8 16 32 MVI D,$32 ; Wait 32 sector times
E9EA CD D0 E9 CALL $E9D0 ; Wait
E9ED C3 F5 E9 JMP $E9F5 ; And select drove
E9F0 3A 03 20 LDA $2003 ; Get last drive
E9F3 B9 CMP C ; Same drive?
E9F4 C8 RZ ; Yes, no need to wait
E9F5 0A LDAX B ; Select new drive
E9F6 79 MOV A,C ; Get drive ID
E9F7 32 03 20 STA $2003 ; Set new flag
E9FA 16 0D MVI D,$0D ; Wait 13 sector tiems
E9FC C3 D0 E9 JMP $E9D0 ; Wait & return
E9FF 00 NOP
--
-John
email: john_crane_Z@yahoodotcom
where: Z=12*5-1
Herbert Johnson
Aug 14, 2012, 10:14:04 AM8/14/12
to
On Tuesday, August 7, 2012 7:01:24 PM UTC-4, John Crane wrote:
> ;
>
> ; North-Star MDS-A disk boot rom disassembly
>
> ;
I assume I can make this code available at no charge on my Web site. Thanks for the work.
> ;
>
> ; North-Star MDS-A disk boot rom disassembly
>
> ;
Herb Johnson
retrotechnology.com
Clu
Dec 26, 2012, 10:11:48 AM12/26/12
to
That is pretty cool. My Dad used to have it where all the load
commands were under a button or two. Used it to access the disk system.
Doc Clu
commands were under a button or two. Used it to access the disk system.
Doc Clu
Clu
Feb 2, 2015, 10:00:47 AM2/2/15
to
This is awesome!! Thanks!
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