Changeset 258 in xtideuniversalbios for trunk/XTIDE_Universal_BIOS/Src/VariablesAndDPTs/RamVars.asm

Timestamp:

Feb 22, 2012, 7:01:53 PM (13 years ago)

Author:

gregli@…

google:author:

gregli@hotmail.com

Message:

Added floppy drive emulation over the serial connection (MODULE_SERIAL_FLOPPY). Along the way, various optimizations were made to stay within the 8K ROM size target. Also, serial code now returns the number of sectors transferred.

File:

• trunk/XTIDE_Universal_BIOS/Src/VariablesAndDPTs/RamVars.asm (modified) (5 diffs)

trunk/XTIDE_Universal_BIOS/Src/VariablesAndDPTs/RamVars.asm

@@ -123 +123 @@
 ;       DS:     RAMVARS segment
 ;   Returns:
-;       CF:     Set if function is handled by this BIOS
-;               Cleared if function belongs to some other BIOS
+;       CF:     Cleared if function is handled by this BIOS
+;               Set if function belongs to some other BIOS
 ;   Corrupts registers:
 ;       Nothing
@@ -131 +131 @@
 RamVars_IsFunctionHandledByThisBIOS:
     test    ah, ah          ; Reset for all floppy and hard disk drives?
-    jz      SHORT .FunctionIsHandledByOurBIOS
-    cmp     ah, 08h         ; Read Disk Drive Parameters?
-    jne     SHORT RamVars_IsDriveHandledByThisBIOS
-    test    dl, dl          ; We do not handle floppy drives
-    jns     SHORT .FunctionIsNotHandledByOurBIOS
-ALIGN JUMP_ALIGN
-.FunctionIsHandledByOurBIOS:
-    stc
-.FunctionIsNotHandledByOurBIOS:
-    ret
-
+    jz      SHORT RamVars_IsDriveHandledByThisBIOS.CFAlreadyClear_IsHandledByOurBIOS
+    cmp     ah, 08h
+%ifdef MODULE_SERIAL_FLOPPY
+; we handle all traffic for function 08h, as we need to wrap both hard disk and floppy drive counts
+    je      SHORT RamVars_IsDriveHandledByThisBIOS.CFAlreadyClear_IsHandledByOurBIOS
+%else
+; we handle all *hard disk* traffic for function 08h, as we need to wrap the hard disk drive count
+    je      SHORT RamVars_IsDriveHandledByThisBIOS.IsDriveAHardDisk
+%endif
+;;; fall-through            
+        
 ;--------------------------------------------------------------------
 ; Checks if drive is handled by this BIOS.
@@ -150 +150 @@
 ;       DS:     RAMVARS segment
 ;   Returns:
-;       CF:     Set if drive is handled by this BIOS
-;               Cleared if drive belongs to some other BIOS
+;       CF:     Cleared if drive is handled by this BIOS
+;               Set if drive belongs to some other BIOS
 ;   Corrupts registers:
 ;       Nothing
@@ -158 +158 @@
 RamVars_IsDriveHandledByThisBIOS:
     push    ax
-    mov     ax, [RAMVARS.wDrvCntAndFirst]       ; Drive count to AL, First number to AH
-    add     al, ah                              ; One past last drive to AL
-    cmp     dl, al                              ; Above last supported?
-    jae     SHORT .DriveNotHandledByThisBIOS
-    cmp     ah, dl                              ; Below first supported?
-    ja      SHORT .DriveNotHandledByThisBIOS
-    stc
-.DriveNotHandledByThisBIOS:
+
+    mov     ax, [RAMVARS.wDrvCntAndFirst]       ; Drive count to AH, First number to AL
+    add     ah, al                              ; One past last drive to AH
+    cmp     dl, ah                              ; Above last supported?
+    jae     SHORT .HardDiskIsNotHandledByThisBIOS
+.TestLowLimit:
+    cmp     dl, al                              ; Below first supported?
+    jae     SHORT .CFAlreadyClear_IsHandledByOurBIOS_PopAX  ; note that CF is clear if the branch is taken
+
+.HardDiskIsNotHandledByThisBIOS:
+%ifdef MODULE_SERIAL_FLOPPY
+    call    RamVars_UnpackFlopCntAndFirstToAL
+    cbw                                         ; normally 0h, could be ffh if no drives present
+    adc     ah, al                              ; if no drives present, still ffh (ffh + ffh + 1 = ffh)
+    js      SHORT .DiskIsNotHandledByThisBIOS
+    cmp     ah, dl
+    jz      SHORT .CFAlreadyClear_IsHandledByOurBIOS_PopAX
+    cmp     al, dl
+    jz      SHORT .CFAlreadyClear_IsHandledByOurBIOS_PopAX
+.DiskIsNotHandledByThisBIOS:            
+%endif
+
+    stc                                         ; Is not supported by our BIOS
+        
+.CFAlreadyClear_IsHandledByOurBIOS_PopAX:               
     pop     ax
-    ret
-
-
-;--------------------------------------------------------------------
-; RamVars_GetHardDiskCountFromBDAtoCX
-;   Parameters:
-;       DS:     RAMVARS segment
-;   Returns:
-;       CX:     Total hard disk count
-;   Corrupts registers:
-;       Nothing
-;--------------------------------------------------------------------
-ALIGN JUMP_ALIGN
-RamVars_GetHardDiskCountFromBDAtoCX:
+.CFAlreadyClear_IsHandledByOurBIOS: 
+    ret
+
+%ifndef MODULE_SERIAL_FLOPPY        
+;
+; Note that we could have just checked for the high order bit in dl, but with the needed STC and jumps, 
+; leveraging the code above resulted in space savings.
+;
+.IsDriveAHardDisk:      
+    push    ax                                  ; match stack at the top of routine
+    mov     al, 80h                             ; to catch all hard disks, lower limit is 80h vs. bFirstDrv
+    jmp     .TestLowLimit                       ; and there is no need to test a high limit
+%endif
+
+;--------------------------------------------------------------------
+; RamVars_GetHardDiskCountFromBDAtoAX
+;   Parameters:
+;       DS:     RAMVARS segment
+;   Returns:
+;       AX:     Total hard disk count
+;   Corrupts registers:
+;       CX
+;--------------------------------------------------------------------
+ALIGN JUMP_ALIGN
+RamVars_GetHardDiskCountFromBDAtoAX:
     push    es
-    push    dx
-
-    LOAD_BDA_SEGMENT_TO es, cx, !       ; Zero CX
-    call    RamVars_GetCountOfKnownDrivesToDL
+
+    LOAD_BDA_SEGMENT_TO es, ax
+    call    RamVars_GetCountOfKnownDrivesToAX
     mov     cl, [es:BDA.bHDCount]
-    MAX_U   cl, dl
-
-    pop     dx
+    MAX_U   al, cl
+        
     pop     es
     ret
 
 ;--------------------------------------------------------------------
-; RamVars_GetCountOfKnownDrivesToDL
-;   Parameters:
-;       DS:     RAMVARS segment
-;   Returns:
-;       DL:     Total hard disk count
-;   Corrupts registers:
-;       Nothing
-;--------------------------------------------------------------------
-ALIGN JUMP_ALIGN
-RamVars_GetCountOfKnownDrivesToDL:
-    mov     dl, [RAMVARS.bFirstDrv]     ; Number for our first drive
-    add     dl, [RAMVARS.bDrvCnt]       ; Our drives
-    and     dl, 7Fh                     ; Clear HD bit for drive count
-    ret
-
-
+; RamVars_GetCountOfKnownDrivesToAX
+;   Parameters:
+;       DS:     RAMVARS segment
+;   Returns:
+;       AX:     Total hard disk count
+;   Corrupts registers:
+;       None
+;--------------------------------------------------------------------
+ALIGN JUMP_ALIGN
+RamVars_GetCountOfKnownDrivesToAX:
+    mov     ax, [RAMVARS.wDrvCntAndFirst]
+    add     al, ah
+    and     al, 7fh
+    cbw
+    ret
+    
 ;--------------------------------------------------------------------
 ; RamVars_GetIdeControllerCountToCX
@@ -219 +245 @@
 ;       Nothing
 ;--------------------------------------------------------------------
+ALIGN JUMP_ALIGN
 RamVars_GetIdeControllerCountToCX:
     eMOVZX  cx, BYTE [cs:ROMVARS.bIdeCnt]
     ret
+
+%ifdef MODULE_SERIAL_FLOPPY
+;--------------------------------------------------------------------
+; RamVars_UnpackFlopCntAndFirstToAL
+;   Parameters:
+;       Nothing
+;   Returns:
+;       AL:     First floppy drive number supported
+;       CF:     Number of floppy drives supported (clear = 1, set = 2)
+;   Corrupts registers:
+;       Nothing
+;--------------------------------------------------------------------       
+ALIGN JUMP_ALIGN
+RamVars_UnpackFlopCntAndFirstToAL:
+    mov     al, [RAMVARS.xlateVars+XLATEVARS.bFlopCntAndFirst]
+    sar     al, 1       
+    ret
+%endif