f12to16.asm

德国Hyperstone公司dsp的CF卡驱动程序

;*************************************************************
;
;  hyperstone MS-DOS FAT File System Drivers
;
;  Conversion routines for 12 bit FAT
;
;  Christoph Baumhof 2000-03-21
;  Reinhard K乭ne 2000-03-21
;  Mihajlo Varga 2000-03-21
;
;  Copyright (C) 1997-2000 hyperstone electronics GmbH Konstanz
;
;  2000-03-21 initial release
;
; $Id$
;
; $Log$
;
;*************************************************************
;
; Changes:
;
;*************************************************************


              segment code

              XDEF    __fat12to16
              XDEF    __fat16to12

__fat12to16:
              FRAME   L7, L2
	      MOV     L4, L0
              SHRI    L4, 1
              ADD     L4, L0
              ADD     L4, L1
              LDBU.D  L4, L5, 0
              LDBU.D  L4, L6, 1
              SHLI    L6, 8
              OR      L6, L5
	      CMPBI   L0, 1
	      BNZ     odd
	      MASK    L6, L6, $FFF
fat12to16exit:
	      CMPI    L6, $ff8
	      BST     fat12to16exit1
	      ADDI    L6, $f000
fat12to16exit1:
	      MOV     L0, L6
	      RET     PC, L2

odd:          SHRI    L6, 4
	      BR      fat12to16exit

__fat16to12:
	      FRAME   L7, L3
              MOV     L5, L0
              SHRI    L5, 1
              ADD     L5, L0
              ADD     L5, L1
              CMPBI   L0, 1
              BNZ     odd1
              LDBU.D  L5, L6, 1
              MASK    L6, L6, $F0
              SHLI    L6, 8
              MASK    L2, L2, $0FFF
              BR      ok
odd1:
              LDBU.D  L5, L6, 0
              SHLI    L2, 4
              MASK    L6, L6, $0F
ok:
              OR      L6, L2
              STBU.D  L5, L6, 0
              SHRI    L6, 8
              STBU.D  L5, L6, 1
              RET     PC, L3

              END