ATMEL公司24系列EEPROM编程举例.doc

ATMEL公司24系列EEPROM编程举例作者：尘封往事 文章来源：本站原创 点击数： 2043 更新时间：2006-1-12 13:07:34 NAMEControl_AT24Cxx ; This collection of routines allows an AT89C2051 microcontroller to read; and write the AT24Cxx family of serial CMOS EEPROMS. This version of the; code is compatible only with the AT89C2051 due to the location of the; data buffer and stack in RAM. The code may be modified to work with the; AT89C1051 by relocating or resizing the buffer and stack to fit into the; smaller amount of RAM available in the AT89C1051. Note that the minimum; size of the buffer is determined by the page size of the AT24Cxx.; All five AT24Cxx device operations are supported. Byte Write, Current; Address Read and Random Read are implemented by the functions WRITE_BYTE,; READ_CURRENT and READ_RANDOM, respectively. Page Write and Sequential Read; are special cases of functions WRITE_BLOCK and READ_BLOCK, respectively.; WRITE_BLOCK and READ_BLOCK process from one byte to the number of bytes; in a page and transfer data between the AT24Cxx and the RAM buffer.; The code supports multiple AT24Cxx devices per bus, each with a unique; address determined by the wiring of the address pins (A0, A1, A2). The; three-bit programmable address is passed to the WRITE_BYTE, READ_CURRENT,; READ_RANDOM, WRITE_BLOCK and READ_BLOCK functions, where it is combined; with the AT24Cxx fixed address (FADDR) and used to address a device on the; bus. Refer to the AT24Cxx family data sheets for additional information on; device addressing.; Functions BYTE_FILL, VERIFY_BYTE_FILL, PAGE_FILL and VERIFY_PAGE_FILL are; artifacts from the debug process and serve to illustrate the use of the; device read and write functions with an AT24C64. To modify the code for a; different member of the AT24Cxx family, simply redefine the values of SIZE; (the number of bytes per device) and PSIZE (the number of bytes per page).; To change the fill value, redefine FILL. To change the programmable portion; of the device address, redefine PADDR to a value from zero to seven.; The code meets all AT24Cxx family timing requirements when executed by an; AT89Cx051 microcontroller with a 12 MHz clock. Code modifications may be; required if a faster clock is substituted.FADDREQU0a0h; fixed address for AT24Cxx EEPROMsPADDREQU0; programmable address (0.7)SIZEEQU2000h; bytes per AT24C64PSIZEEQU32; bytes per page for AT24C64FILLEQU55h; example fill value; Register definitions.indexEQUr0; buffer pointerkountEQUr1; byte count registerzdataEQUr1; data registeraddr_loEQUr2; 2-byte address registeraddr_hiEQUr3; Microcontroller connections to AT24Cxx serial bus lines.SCLBITp1.2; serial clockSDABITp1.3; serial dataDSEG AT 20HORG40Hbuffer:DSPSIZE; storage for read/write dataORG60H; stack originstack:DS20H; stack depthCSEGORG0000H; power on/reset vectorjmpon_resetORG0003H; external interrupt 0 vectorreti; undefinedORG000BH; timer 0 overflow vectorreti; undefinedORG0013H; external interrupt 1 vectorreti; undefinedORG001BH; timer 1 overflow vectorreti; undefinedORG0023H; serial I/O interrupt vectorreti; undefinedORG0080H; begin code spaceUSING0; register bank zeroon_reset:movsp, #(stack-1); initialize stack pointer; Initialize AT24Cxx serial bus lines.setbSDA; highsetbSCL; highcallbyte_filljcfaultcallverify_byte_filljcfaultcallpage_filljcfaultcallverify_page_filljcfaultfault:jmp$byte_fill:; Fill every byte in an AT24Cxx with the same value.; Writes one address at a time (page mode is not used).; Returns CY set to indicate write timeout.; Destroys A, B, DPTR, XDATA, ADDR_HI:ADDR_LO.movzdata, #FILL; set up fill datamovdptr, #0; initialize address pointerx51:movaddr_lo, dpl; set up addressmovaddr_hi, dph;movb, #120; retry counterx52:mova, #PADDR; programmable addresscallwrite_byte; try to writejncx53; jump if write OKdjnzb, x52; try againsetbc; set timeout error flagjmpx54; exitx53:incdptr; advance address pointer;mova, dpl; check low byte;cjnea, #(LOW SIZE), x51; jump if not lastmova, dph; check high bytecjnea, #(HIGH SIZE), x51; jump if not lastclrc; clear error flagx54:retverify_byte_fill:; Verify that all bytes in an AT24Cxx match a fill value.; Reads and verifies one byte at a time (page mode is not used).; Performs a Random Read function to initialize the internal; address counter and checks the contents of the first address.; Then performs multiple Current Address Read functions to step; through the remaining addressess.; Returns CY set to indicate read timeout or compare fail.; Destroys A, B, DPTR.movdptr, #0; initialize address pointer/countermovaddr_lo, dpl; set up addressmovaddr_hi, dph;movb, #120; retry counterx81:mova, #PADDR; programmable addresscallread_random; try to readjncx82; jump if read OKdjnzb, x81; try againjmpx86; set error flag and exitx82:cjnea, #FILL, x86; jump if compare errorjmpx85; do remaining addressesx83:mova, #PADDRcallread_currentjcx87; jump if read failscjnea, #FILL, x86; jump if compare errorx85:incdptr; advance address pointermova, dph; check high bytecjnea, #(HIGH SIZE), x83; jump if not lastclrc; clear error flagjmpx87; exitx86:setbc; set error flagx87:retpage_fill:; Fill every byte in an AT24Cxx with the same value.; Writes one page at a time.; Returns CY set to indicate write timeout.; Destroys A, B, DPTR, KOUNT, INDEX, ADDR_HI:ADDR_LO.; First fill buffer.movb, #PSIZE; bytes per pagemovindex, #buffer; point to bufferx61:movindex, #FILL; put fill value in bufferincindex; advance pointerdjnzb, x61; next byte; Copy buffer to device, one page at a time.movdptr, #0; initialize address pointerx62:movaddr_lo, dpl; set up addressmovaddr_hi, dph;movkount, #PSIZE; bytes per pagemovb, #120; retry counterx63:mova, #PADDR; programmable addresscallwrite_block; try to writejncx64; jump if write OKdjnzb, x63; try againsetbc; set timeout error flagjmpx66; exitx64:; Add page size to address pointer.mova, dpl; get low byteadda, #PSIZE; add page sizemovdpl, a; save low bytejncx65; jump if high byte not affectedincdph; increment high bytex65:;cjnea, #(LOW SIZE), x62; jump if low byte not lastmova, dph; check high bytecjnea, #(HIGH SIZE), x62; jump if not lastclrc; clear error flagx66:retverify_page_fill:; Verify that all bytes in an AT24Cxx match a fill value.; Reads and verifies one page at a time.; Returns CY set to indicate read timeout or compare fail.; Destroys A, B, DPTR, KOUNT, INDEX, ADDR_HI:ADDR_LO.; Copy device page to buffer.movdptr, #0; initialize address pointerx71:movaddr_lo, dpl; set up addressmovaddr_hi, dph;movkount, #PSIZE; bytes per pagemovb, #120; retry counterx72:mova, #PADDR; programmable addresscallread_block; try to readjncx74; jump if read OKdjnzb, x72; try againx73:setbc; set error flagjmpx77; exitx74:; Verify buffer contents.movb, #PSIZE; bytes per pagemovindex, #buffer; point to bufferx75:cjneindex, #FILL, x73; jump if compare failsincindex; advance pointerdjnzb, x75; next byte; Add page size to address pointer.mova, dpl; get low byteadda, #PSIZE; add page sizemovdpl, a; save low bytejncx76; jump if high byte not affectedincdph; increment high bytex76:;cjnea, #(LOW SIZE), x71; jump if low byte not lastmova, dph; check high bytecjnea, #(HIGH SIZE), x71; jump if not lastclrc; clear error flagx77:retwrite_block:; Write from one byte to one page of data to an AT24Cxx.; Called with programmable address in A, address of first byte; in register pair ADDR_HI:ADDR_LO, data in BUFFER, byte count; in register KOUNT.; Does not wait for write cycle to complete.; Returns CY set to indicate that the bus is not available; or that the addressed device failed to acknowledge.; Destroys A, KOUNT, INDEX.callstartjcx38; abort if bus not availablerla; programmable address to bits 3:1orla, #FADDR; add fixed addressclracc.0; specify write operationcallshout; send device addressjcx37; abort if no acknowledgemova, addr_hi; send high byte of addresscallshout;jcx37; abort if no acknowledgemova, addr_lo; send low byte of addresscallshout;jcx37; abort if no acknowledgemovindex, #buffer; point to bufferx36:mova, index; get datacallshout; send datajcx37; abort if no acknowledgeincindex; advance buffer pointerdjnzkount, x36; next byteclrc; clear error flagx37:callstopx38:retread_block:; Read from one byte to one page of data from an AT24Cxx.; Performs a Random Read which is extended into a Sequential Read; when more than one byte is read. Called with programmable address; in A, address of first byte in register pair ADDR_HI:ADDR_LO,; byte count in register KOUNT.; Returns data in BUFFER. Returns CY set to indicate that the bus is; not available or that the addressed device failed to acknowledge.; Destroys A, KOUNT, INDEX.; Send dummy write command to address first byte.callstartjcx35; abort if bus not availablerla; programmable address to bits 3:1orla, #FADDR; add fixed addressmovindex, a; save copy of device addressclracc.0; specify write operationcallshout; send device addressjcx34; abort if no acknowledgemova, addr_hi; send high byte of addresscallshout;jcx34; abort if no acknowledgemova, addr_lo; send low byte of addresscallshout;jcx34; abort if no acknowledge; Send read command and receive data.callstart; second start for readjcx34; abort if bus not availablemova, index; get device addresssetbacc.0; specify read operationcallshout; send device addressjcx34; abort if no acknowledgemovindex, #buffer; point to bufferx31:callshin; receive data bytemovindex, a; save datacjnekount, #1, x32; jump if not last bytecallNAK; do not acknowledge last bytejmpx33; donex32:callACK; acknowledge byteincindex; advance buffer pointerdjnzkount, x31; next bytex33:clrc; clear error flagx34:callstopx35:retwrite_byte:; AT24Cxx Byte Write function.; Called with programmable address in A, byte address in; register pair ADDR_HI:ADDR_LO, data in register XDATA.; Does not wait for write cycle to complete.; Returns CY set to indicate that the bus is not available; or that the addressed device failed to acknowledge.; Destroys A.callstartjcx49; abort if bus not availablerla; programmable address to bits 3:1orla, #FADDR; add fixed addressclracc.0; specify write operationcallshout; send device addressjcx48; abort if no acknowledgemova, addr_hi; send high byte of addresscallshout;jcx48; abort if no acknowledgemova, addr_lo; send low byte of addresscallshout;jcx48; abort if no acknowledgemova, zdata; get datacallshout; send datajcx48; abort if no acknowledgeclrc; clear error flagx48:callstopx49:retread_current:; AT24Cxx Current Address Read function.; Called with programmable address in A. Returns data in A.; Returns CY set to indicate that the bus is not available; or that the addressed device failed to acknowledge.callstartjcx45; abort if bus not availablerla; programmable address to bits 3:1orla, #FADDR; add fixed addresssetbacc.0; specify read operationcallshout; send device addressjcx44; abort if no acknowledgecallshin; receive data bytecallNAK; do not acknowledge byteclrc; clear error flagx44:callstopx45:retread_random:; AT24Cxx Random Read function.; Called with programmable address in A, byte address in; register pair ADDR_HI:ADDR_LO. Returns data in A.; Returns CY set to indicate that the bus is not available; or that the addressed device failed to acknowledge.pushbmovb, a; save copy of programmable address; Send dummy write command to set internal address.callstartjcx47; abort if bus not availablerla; programmable address to bits 3:1orla, #FADDR; add fixed addressclracc.0; specify write operationcallshout; send device addressjcx46; abort if no acknowledgemova, addr_hi; send high byte of addresscallshout;jcx46; abort if no acknowledgemova, addr_lo; send low byte of addresscallshout;jcx46; abort if no acknowledge; Call Current Address Read function.mova, b; get programmable addresscallread_currentjmpx47; exitx46:callstopx47:popbretstart:; Send START, defined as high-to-low SDA with SCL high.; Return with SCL, SDA low.; Returns CY set if bus is not available.setbSDAsetbSCL; Verify bus available.jnbSDA, x40; jump if not highjnbSCL, x40; jump if not highnop; enforce setup delay and cycle delayclrSDAnop; enforce hold delaynop;nop;nop;nop;clrSCLclrc; clear error flagjmpx41x40:setbc; set error flagx41:retstop:; Send STOP, defined as low-to-high SDA with SCL high.; SCL expected low on entry. Return with SCL, SDA high.clrSDAnop; enforce SCL low and data setupnopsetbSCLnop; enforce setup delaynop;nop;nop;nop;setbSDAretshout:; Shift out a byte to the AT24Cxx, most significant bit fir