| 1 | ; Project name : XTIDE Universal BIOS
|
|---|
| 2 | ; Description : Functions for hard disk capacity calculations.
|
|---|
| 3 |
|
|---|
| 4 | ; Section containing code
|
|---|
| 5 | SECTION .text
|
|---|
| 6 |
|
|---|
| 7 | ;--------------------------------------------------------------------
|
|---|
| 8 | ; Calculates sector count from L-CHS values returned by INT 13h, AH=08h.
|
|---|
| 9 | ;
|
|---|
| 10 | ; HCapacity_GetSectorCountFromForeignAH08h:
|
|---|
| 11 | ; HCapacity_GetSectorCountFromOurAH08h:
|
|---|
| 12 | ; Parameters:
|
|---|
| 13 | ; DL: Drive number
|
|---|
| 14 | ; DS: RAMVARS segment
|
|---|
| 15 | ; Returns:
|
|---|
| 16 | ; DX:AX: Total sector count
|
|---|
| 17 | ; BX: Zero
|
|---|
| 18 | ; Corrupts registers:
|
|---|
| 19 | ; CX
|
|---|
| 20 | ;--------------------------------------------------------------------
|
|---|
| 21 | ALIGN JUMP_ALIGN
|
|---|
| 22 | HCapacity_GetSectorCountFromForeignAH08h:
|
|---|
| 23 | mov ah, 08h ; Get Drive Parameters
|
|---|
| 24 | call Int13h_CallPreviousInt13hHandler
|
|---|
| 25 | jmp SHORT HCapacity_ConvertAH08hReturnValuesToSectorCount
|
|---|
| 26 |
|
|---|
| 27 | ALIGN JUMP_ALIGN
|
|---|
| 28 | HCapacity_GetSectorCountFromOurAH08h:
|
|---|
| 29 | push di
|
|---|
| 30 | call AH8h_GetDriveParameters
|
|---|
| 31 | pop di
|
|---|
| 32 | ; Fall to HCapacity_ConvertAH08hReturnValuesToSectorCount
|
|---|
| 33 |
|
|---|
| 34 | ALIGN JUMP_ALIGN
|
|---|
| 35 | HCapacity_ConvertAH08hReturnValuesToSectorCount:
|
|---|
| 36 | call HAddress_ExtractLCHSFromBiosParams
|
|---|
| 37 | xor ax, ax ; Zero AX
|
|---|
| 38 | inc cx ; Max cylinder number to cylinder count
|
|---|
| 39 | xchg al, bh ; AX=Max head number, BX=Sectors per track
|
|---|
| 40 | inc ax ; AX=Head count
|
|---|
| 41 | mul bx ; AX=Head count * Sectors per track
|
|---|
| 42 | mul cx ; DX:AX = Total sector count
|
|---|
| 43 | xor bx, bx ; Zero BX for 48-bit sector count (and clear CF)
|
|---|
| 44 | ret
|
|---|
