cf_routines.asm

TI 5402 dsp芯片读写cf卡的源程序

* Routine to issue commands to the CompactFlash.
*  * initializes the Sector Count, Sector Number, Cylinder High/Low,
*    Card/Head, and Command Registers
*  * uses bitwise AND and OR operations to set the LBA
**********************************************************************

_CF_IssueCommand:
	
	RSBX SXM			;disable sign extension -RDP-

	STL A, *(PhySector+1)		;save first arg (PhysicalSector) in LBA
	STH A, *(PhySector)
	nop
	nop
	nop
	nop
	
	LD *SP(1), A			;load arg SectorCount in A
	STL A, *(SectCnt)		;save SectorCount in SectCnt
	LD *SP(2), A			;load arg Command in A
	STL A, *(Command)		;save Command in variable Command

**** write sector count register
	
	ATARegWrite SectCnt, SectCntReg
	
**** initialize A Accumulator with low word in variable LBA

	LD *(PhySector+1), A

**** load Sector Number Register
			 
	LD #0x000000FF, B		
	AND A, B			;clear unwanted bits
	STL B, *(SectNum)       	;save in SectNum
	ATARegWrite SectNum, SectNumReg
			            
**** load Cylinder Low Register            
            
	LD #0x0000FF00, B
	AND A, B          		;clear unwanted bits
	STL B, -8, *(CylnLow)		;save in CylnLow
	ATARegWrite CylnLow, CylnLowReg
			 
**** initialize A Accumulator with high word in variable LBA

	LD *(PhySector), A
			
**** load Cylinder High Register
			
	LD #0x000000FF, B
	AND A, B           		;clear unwanted bits
	STL B, *(CylnHigh)		;save in CylnHigh
	ATARegWrite CylnHigh, CylnHighReg

**** load Card/Head Register

	LD #0x0000000F, B 
	AND A,-8, B			;clear unwanted bits
	LD #0xe0, A			;LBA = 1, DRV = 0
					; LBA(27-24) = 0
	OR A, B                 
	STL B, *(CrdHead)		;initalize LBA(27-24)
	ATARegWrite CrdHead, CrdHeadReg
	
**** write command register

	ATARegWrite Command, CommandReg 
	RET	

**********************************************************************
* _ReadCF
* Read from the CompactFlash
* 
*  * issue read command
*  * if Sector Count Register = 0 => 256 sectors to transfer
*  * A: Check DRQ
*  * read 1 sector
*  * multiple sector transfers? continue from A: 
**********************************************************************

_ReadCF:
    
***** Prepare the parameters that are to be passed to _CF_IssueCommand

	LD *(_CReadSectors), B		;_CReadSectors
	NOP				;clear pipeline conflict
	PSHM BL				;push Command on stack
	LD *SP(1), B			;load SectorCount in B
	NOP	
	PSHM BL				;push SectorCount on stack
	STLM B, AR4			;store SectorCount in AR4
	STM #0, AR0			;store zero in AR0
	
***** Determine the number of sectors that are to be transferred

	CMPR EQ, AR4			;SectorCount = 0?
					;TC=1 Yes
					;TC=0 No
	NOP				;NOP to prepare for XC
	XC 2, TC			;If SectorCount = 0
	STM #256, AR3			; XferSectors = 256
	XC 2, NTC			;Else
	STLM B, AR3			; XferSectors = SectorCount
	NOP

***** Issue the Read Sectors Command

	CALL _CF_IssueCommand		;issue Read Sectors command
	POPM BL				;pop SectorCount off stack
	POPM BL				;pop _CReadSectors off stack    
    
***** the BANZ mnemonic checks XferSectors at the end of the 
***** read process.  XferSectors must be subtracted by one so
***** that the correct number of sectors are transferred
    
	LDM AR3, B					
	SUB #1, B			;XferSectors = XferSectors-1
	STLM B, AR3
    					
***** Read from the CompactFlash
    
read_outer:

	CALL _CF_CheckDrqStatus		;CF ready for data transfer?
    
	STM #ReadBuffer, AR5		;AR5 = ReadBuffer (beginning address)
	RPT #255					
	PORTR #WrdDataReg, *AR5+	;read 256 words 
					; (1 sector = 512 bytes)
					; from the CF Data 
					; Register 

**********************************************************************
* - the data read into ReadBuffer should be processed at this point
* - array ReadBuffer will be overwritten during multiple sector
*    transfers
**********************************************************************	 							
	 							
	BANZ read_outer, *AR3-		;loop until all sectors have been 
					; transferred
	
	CALL _CF_CheckBusyStatus
	RET
	
**********************************************************************
* _WriteCF
**********************************************************************

_WriteCF:
    
***** Prepare the parameters that are to be passed to _CF_IssueCommand

	LD *(_CWriteSectors), B		;_CWriteSectors
	NOP				;clear pipeline conflict
	PSHM BL				;push Command on stack
	LD *SP(1), B	   		;load SectorCount in B
	NOP
	PSHM BL				;push SectorCount on stack
	STLM B, AR4			;store SectorCount in AR4
	STM #0, AR0			;store zero in AR0
	
***** Determine the number of sectors that are to be transferred

	CMPR EQ, AR4			;SectorCount = 0?
					;TC=1 Yes
					;TC=0 No
	NOP				;NOP to prepare for XC
	XC 2, TC			;If SectorCount = 0
	STM #256, AR3			; XferSectors = 256
	XC 2, NTC			;Else
	STLM B, AR3			; XferSectors = SectorCount
	NOP

***** Issue the Write Sectors Command

	CALL _CF_IssueCommand		;issue Write Sectors command
	POPM BL				;pop SectorCount off stack
    POPM BL				;pop _CWriteSectors off stack    
    
***** the BANZ mnemonic checks XferSectors at the end of the 
***** read process.  XferSectors must be subtracted by one so
***** that the correct number of sectors are transferred
    
	LDM AR3, B					
	SUB #1, B			;XferSectors = XferSectors-1
	STLM B, AR3
    					
***** Write to the CompactFlash
    
write_outer:

	CALL _CF_CheckDrqStatus		;CF ready for data transfer?
    addm #1,*(WriteBuffer)
	STM #WriteBuffer, AR5		;AR5 = WriteBuffer (beginning address)
	STM #255,BRC
	RPTB WRITE_DATA-1					
	PORTW *AR5+, #WrdDataReg	;read 256 words 
	 				; (1 sector = 512 bytes)
	 				; from the CF Data 
					; Register 
	NOP
WRITE_DATA:
**********************************************************************
* - the data written into WriteBuffer should be updated with new
*	data here.  This updated data will be written to the CompactFlash.
*	if WriteBuffer is not updated, the previous data will be duplicated
*	in the CompactFlash
**********************************************************************	 							
	nop
	nop 
					
	BANZ write_outer, *AR3-		;loop until all sectors have been 
					; transferred

	CALL _CF_CheckBusyStatus
									
	RET
	
**********************************************************************
* _CF_CheckErrorStatus
* Routine to check the ERR bit in the Status Register
*   if ERR = 1, read the Error Register, save state in 
*   ErrorSt, and exit
**********************************************************************	 								
	
_CF_CheckErrorStatus:

	ST #0, *(ErrorSt)		;initialize ErrorSt to zero
    	PORTR #StatusReg, *(Status)	;read status register
    	STM #Status, AR2		;AR2=Status
    
***** ERR = 1?
	
	BIT*AR2, #15-0			;TC = D0 = ERR bit    
	NOP
	NOP
	BC No_Error, NTC		;ERR = 0 => end routine
					;ERR = 1 => read error register
	
Error:

	PORTR #ErrorReg, *(ErrorSt)	;read error register and save state
	NOP
	NOP
	B C$$EXIT			;exit
	
No_Error:		
	
	RET       
	
**********************************************************************
* _CF_Present
* This routine checks to see if the CompactFlash is properly 
* inserted in its socket. Since this code is not written to
* support hotplug, the status is only checked once. If the 
* card is not present then the system will have to be powered 
* down for card insertion.
* If the card is deteced, the function returns a true value, 
* otherwise a false value is returned.
* - This routine should be modified to handle specific system 
*	requirements
**********************************************************************	 		
	   
_CF_Present:
	LD #0, A			;Set return value to false	
	BC not_inserted, NBIO		;BIO = 1 => CF not inserted correctly
					;BIO = 0 => CF inserted correctly
	NOP
	NOP 
	LD #1, A			;Set return value to true	
	RET				;Card present, return normally

not_inserted:				;Card not present 
	RET				;exit
**********************************************************************
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