Changeset 551 in xtideuniversalbios for trunk/XTIDE_Universal_BIOS/Src/Device

Timestamp:

Jun 6, 2013, 3:31:51 PM (11 years ago)

Author:

aitotat@…

google:author:

aitotat@gmail.com

Message:

Changes to XTIDE Universal BIOS:

• DMA fixes by James Pearce.
• Interrupt handlers are now installed before starting to detect drives (HotkeyBar require INT 40h handler for correct drive letters).

File:

• trunk/XTIDE_Universal_BIOS/Src/Device/IDE/IdeDmaBlock.asm (modified) (4 diffs)

trunk/XTIDE_Universal_BIOS/Src/Device/IDE/IdeDmaBlock.asm

@@ -1 +1 @@
 ; Project name  :   XTIDE Universal BIOS
 ; Description   :   IDE Read/Write functions for transferring
-;                   block using DMA.
-;                   These functions should only be called from IdeTransfer.asm.
-
+;           block using DMA.
+;           These functions should only be called from IdeTransfer.asm.
+; Modified JJP 05-Jun-13
 ;
 ; XTIDE Universal BIOS and Associated Tools
@@ -19 +19 @@
 ; Visit http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
 ;
-
 
 ; Section containing code
@@ -81 +80 @@
     add     dl, XTCF_CONTROL_REGISTER
 
-    ; Calculate bytes for first page
-    mov     ax, di
-    neg     ax                                      ; AX = Max BYTEs for first page
+    ; convert sectors in CX to BYTES
 %ifdef USE_186
     shl     cx, 9                                   ; CX = Block size in BYTEs
 %else
-    xchg    cl, ch
+    xchg        cl, ch
     shl     cx, 1
 %endif
+
+    ; Calculate bytes for first page
+    mov     ax, di
+    neg     ax          ; 2s compliment
+
+    ; if DI was zero carry flag will be cleared (and set otherwise)
+    ; When DI is zero only one transfer is required since we've limited the
+    ; XT-CFv3 block size to 32k
+    jnc .TransferLastDmaPageWithSizeInCX
+
+    ; CF was set, so DI != 0 and we might need one or two transfers
     cmp     cx, ax                                  ; if we won't cross a physical page boundary...
-    jbe     SHORT .TransferLastDmaPageWithSizeInCX  ; ...perform the transfer in one operation
+    jbe SHORT .TransferLastDmaPageWithSizeInCX  ; ...perform the transfer in one operation
 
     ; Calculate how much we can transfer on first and second rounds
-    xchg    cx, ax                                  ; CX = BYTEs for first page
-    sub     ax, cx                                  ; AX = BYTEs for second page
-    push    ax                                      ; Save bytes for second transfer on stack
+    xchg        cx, ax          ; CX = BYTEs for first page
+    sub     ax, cx          ; AX = BYTEs for second page
+    push        ax          ; Save bytes for second transfer on stack
 
     ; Transfer first DMA page
@@ -111 +119 @@
 ;   Parameters:
 ;       BL:     Byte for DMA Mode Register
-;       CX:     Number of BYTEs to transfer (512...32768 since max block size is limited to 64)
+;       CX:     Number of BYTEs to transfer (1...32768 since max block size is limited to 64)
 ;       DX:     XT-CFv3 Control Register
 ;       ES:     Bits 3..0 have physical address bits 19..16