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Add comments to both Harddisk.cpp & the firmware code about 'sta abs16,x' false-reads, etc. 

Harddisk.cpp: Fix typos and update the notes on the r/w commands' operation.
This commit is contained in:
tomcw 2021-11-11 21:20:54 +00:00
parent 5ed901f720
commit 6282790c3d
2 changed files with 38 additions and 22 deletions
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18
firmware/HDD/hddrvr.a65
View File

@ -49,13 +49,19 @@
; constants ; constants
hd_execute = $c080 hd_execute = $c080
hd_error = $c081 ; b7=busy, b0=error hd_status = $c081 ; b7=busy, b0=error
hd_command = $c082 hd_command = $c082
hd_unitnum = $c083 hd_unitnum = $c083
hd_memblock = $c084 hd_memblock = $c084
hd_diskblock = $c086 hd_diskblock = $c086
;hd_nextbyte = $c088 ; legacy read-only port (still supported by AppleWin) ;hd_nextbyte = $c088 ; legacy read-only port (still supported by AppleWin)
; Notes on accesses to I/O registers:
; . ROR ABS16,X and ROL ABS16,X - only used for $C081+s*$10 STATUS register:
; 6502: double read (old data), write (old data), write (new data). The writes are harmless as writes are ignored to STATUS.
; 65C02: double read (old data), write (new data). The write is harmless as writes are ignored to STATUS.
; . STA ABS16,X does a false-read. This is harmless for writable I/O registers, since the false-read has no side effect.
command = $42 command = $42
unitnum = $43 unitnum = $43
memblock = $44 memblock = $44
@ -168,7 +174,7 @@ Bootstrap2
sta hd_unitnum,x ; b7=0 => disk 1 sta hd_unitnum,x ; b7=0 => disk 1
sta hd_command,x sta hd_command,x
lda hd_execute,x lda hd_execute,x
ror hd_error,x ; Post: C=0 or 1 ror hd_status,x ; Post: C=0 or 1
bcc hdboot bcc hdboot
; no image ready, boot diskette image instead ; no image ready, boot diskette image instead
@ -272,7 +278,7 @@ GetSlotInX
; C=1 => via GetSlotInX (eg. Entrypoint / SmartPort2) ; C=1 => via GetSlotInX (eg. Entrypoint / SmartPort2)
; X = Slot# << 4 ; X = Slot# << 4
; Post: ; Post:
; C = hd_error.b0 ; C = hd_status.b0
; A = result of hd_execute ; A = result of hd_execute
; X = Slot# << 4 ; X = Slot# << 4
cmdproc cmdproc
@ -292,17 +298,17 @@ cmdproc
sta hd_diskblock+1,x sta hd_diskblock+1,x
lda hd_execute,x ; A = result of hd_execute (NB. instantaneous 512 byte r/w!) lda hd_execute,x ; A = result of hd_execute (NB. instantaneous 512 byte r/w!)
- rol hd_error,x ; b7=busy doing DMA? - rol hd_status,x ; b7=busy doing DMA?
bcs - bcs -
plp ; restore C from start of cmdproc plp ; restore C from start of cmdproc
bcs done bcs done
ror hd_error,x ; Post: C=0 or 1 ror hd_status,x ; Post: C=0 or 1
lda #0 lda #0
beq hdboot2 beq hdboot2
done done
ror hd_error,x ; Post: C=0 or 1 ror hd_status,x ; Post: C=0 or 1
rts rts
;====================================== ;======================================

42
source/Harddisk.cpp
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@ -42,54 +42,64 @@ Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
#include "../resource/resource.h" #include "../resource/resource.h"
/* /*
Memory map: Memory map (for slot 7):
C0F0 (r) EXECUTE AND RETURN STATUS C0F0 (r) EXECUTE AND RETURN STATUS
C0F1 (r) STATUS (or ERROR) C0F1 (r) STATUS (or ERROR): b7=busy, b0=error
C0F2 (r/w) COMMAND C0F2 (r/w) COMMAND
C0F3 (r/w) UNIT NUMBER C0F3 (r/w) UNIT NUMBER
C0F4 (r/w) LOW BYTE OF MEMORY BUFFER C0F4 (r/w) LOW BYTE OF MEMORY BUFFER
C0F5 (r/w) HIGH BYTE OF MEMORY BUFFER C0F5 (r/w) HIGH BYTE OF MEMORY BUFFER
C0F6 (r/w) LOW BYTE OF BLOCK NUMBER C0F6 (r/w) LOW BYTE OF BLOCK NUMBER
C0F7 (r/w) HIGH BYTE OF BLOCK NUMBER C0F7 (r/w) HIGH BYTE OF BLOCK NUMBER
C0F8 (r) NEXT BYTE C0F8 (r) NEXT BYTE (legacy read-only port - still supported)
Firmware notes:
. ROR ABS16,X and ROL ABS16,X - only used for $C081+s*$10 STATUS register:
6502: double read (old data), write (old data), write (new data). The writes are harmless as writes to STATUS are ignored.
65C02: double read (old data), write (new data). The write is harmless as writes to STATUS are ignored.
. STA ABS16,X does a false-read. This is harmless for writable I/O registers, since the false-read has no side effect.
*/ */
/* /*
Hard drive emulation in Applewin. Hard drive emulation in AppleWin.
Concept Concept
To emulate a 32mb hard drive connected to an Apple IIe via Applewin. To emulate a 32mb hard drive connected to an Apple IIe via AppleWin.
Designed to work with Autoboot Rom and Prodos. Designed to work with Autoboot Rom and Prodos.
Overview Overview
1. Hard drive image file 1. Hard drive image file
The hard drive image file (.HDV) will be formatted into blocks of 512 The hard drive image file (.HDV) will be formatted into blocks of 512
bytes, in a linear fashion. The internal formatting and meaning of each bytes, in a linear fashion. The internal formatting and meaning of each
block to be decided by the Apple's operating system (ProDos). To create block to be decided by the Apple's operating system (ProDOS). To create
an empty .HDV file, just create a 0 byte file (I prefer the debug method). an empty .HDV file, just create a 0 byte file.
2. Emulation code 2. Emulation code
There are 4 commands Prodos will send to a block device. There are 4 commands ProDOS will send to a block device.
Listed below are each command and how it's handled: Listed below are each command and how it's handled:
1. STATUS 1. STATUS
In the emulation's case, returns only a DEVICE OK (0) or DEVICE I/O ERROR (8). In the emulation's case, returns only a DEVICE OK (0), DEVICE I/O ERROR ($27) or DEVICE NOT CONNECTED ($28)
DEVICE I/O ERROR only returned if no HDV file is selected. DEVICE NOT CONNECTED only returned if no HDV file is selected.
2. READ 2. READ
Loads requested block into a 512 byte buffer by attempting to seek to Loads requested block into a 512 byte buffer by attempting to seek to
location in HDV file. location in HDV file.
If seek fails, returns a DEVICE I/O ERROR. Resets hd_buf_ptr used by HD_NEXTBYTE If seek fails, returns a DEVICE I/O ERROR. Resets m_buf_ptr used by legacy HD_NEXTBYTE
Copies requested block from a 512 byte buffer to the Apple's memory.
Sets STATUS.busy=1 until the DMA operation completes.
Returns a DEVICE OK if read was successful, or a DEVICE I/O ERROR otherwise. Returns a DEVICE OK if read was successful, or a DEVICE I/O ERROR otherwise.
3. WRITE 3. WRITE
Copies requested block from the Apple's memory to a 512 byte buffer Copies requested block from the Apple's memory to a 512 byte buffer
then attempts to seek to requested block. then attempts to seek to requested block.
If the seek fails (usually because the seek is beyond the EOF for the If the seek fails (usually because the seek is beyond the EOF for the
HDV file), the Emulation will attempt to "grow" the HDV file to accomodate. HDV file), the emulation will attempt to "grow" the HDV file to accommodate.
Once the file can accomodate, or if the seek did not fail, the buffer is Once the file can accommodate, or if the seek did not fail, the buffer is
written to the HDV file. NOTE: A2PC will grow *AND* shrink the HDV file. written to the HDV file. NOTE: A2PC will grow *AND* shrink the HDV file.
Sets STATUS.busy=1 until the DMA operation completes.
I didn't see the point in shrinking the file as this behaviour would require I didn't see the point in shrinking the file as this behaviour would require
patching prodos (to detect DELETE FILE calls). patching prodos (to detect DELETE FILE calls).
@ -99,9 +109,9 @@ Overview
3. Bugs 3. Bugs
The only thing I've noticed is that Copy II+ 7.1 seems to crash or stall The only thing I've noticed is that Copy II+ 7.1 seems to crash or stall
occasionally when trying to calculate how many free block are available occasionally when trying to calculate how many free blocks are available
when running a catalog. This might be due to the great number of blocks when running a catalog. This might be due to the great number of blocks
available. Also, DDD pro will not optimise the disk correctally (it's available. Also, DDD pro will not optimise the disk correctly (it's
doing a disk defragment of some sort, and when it requests a block outside doing a disk defragment of some sort, and when it requests a block outside
the range of the image file, it starts getting I/O errors), so don't the range of the image file, it starts getting I/O errors), so don't
bother. Any program that preforms a read before write to an "unwritten" bother. Any program that preforms a read before write to an "unwritten"