ATMEL公司24系列EEPROM编程举例

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 13:07:34NAME Control_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.FADDR EQU 0a0h ; fixed address for AT24Cxx EEPROMsPADDR EQU 0 ; programmable address (0..7)SIZE EQU 2000h ; bytes per AT24C64PSIZE EQU 32 ; bytes per page for AT24C64FILL EQU 55h ; example fill value; Register definitions.index EQU r0 ; buffer pointerkount EQU r1 ; byte count registerzdata EQU r1 ; data registeraddr_lo EQU r2 ; 2-byte address registeraddr_hi EQU r3 ;; Microcontroller connections to AT24Cxx serial bus lines.SCL BIT p1.2 ; serial clockSDA BIT p1.3 ; serial dataDSEG AT 20HORG 40Hbuffer: DS PSIZE ; storage for read/write data ORG 60H ; stack originstack: DS 20H ; stack depthCSEGORG 0000H ; power on/reset vectorjmp on_resetORG 0003H ; external interrupt 0 vectorreti ; undefinedORG 000BH ; timer 0 overflow vectorreti ; undefinedORG 0013H ; external interrupt 1 vectorreti ; undefinedORG 001BH ; timer 1 overflow vectorreti ; undefinedORG 0023H ; serial I/O interrupt vectorreti ; undefinedORG 0080H ; begin code spaceUSING 0 ; register bank zeroon_reset:mov sp, #(stack-1) ; initialize stack pointer ; Initialize AT24Cxx serial bus lines.setb SDA ; highsetb SCL ; highcall byte_filljc faultcall verify_byte_filljc faultcall page_filljc faultcall verify_page_filljc faultfault: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.mov zdata, #FILL ; set up fill datamov dptr, #0 ; initialize address pointerx51:mov addr_lo, dpl ; set up addressmov addr_hi, dph ;mov b, #120 ; retry counterx52:mov a, #PADDR ; programmable addresscall write_byte ; try to writejnc x53 ; jump if write OKdjnz b, x52 ; try againsetb c ; set timeout error flagjmp x54 ; exitx53:inc dptr ; advance address pointer; mov a, dpl ; check low byte; cjne a, #(LOW SIZE), x51 ; jump if not lastmov a, dph ; check high bytecjne a, #(HIGH SIZE), x51 ; jump if not lastclr c ; 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.mov dptr, #0 ; initialize address pointer/counter mov addr_lo, dpl ; set up addressmov addr_hi, dph ;mov b, #120 ; retry counterx81:mov a, #PADDR ; programmable addresscall read_random ; try to readjnc x82 ; jump if read OKdjnz b, x81 ; try againjmp x86 ; set error flag and exitx82:cjne a, #FILL, x86 ; jump if compare errorjmp x85 ; do remaining addressesx83:mov a, #PADDRcall read_currentjc x87 ; jump if read failscjne a, #FILL, x86 ; jump if compare errorx85:inc dptr ; advance address pointermov a, dph ; check high bytecjne a, #(HIGH SIZE), x83 ; jump if not lastclr c ; clear error flagjmp x87 ; exitx86:setb c ; 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.mov b, #PSIZE ; bytes per pagemov index, #buffer ; point to bufferx61:mov @index, #FILL ; put fill value in bufferinc index ; advance pointerdjnz b, x61 ; next byte; Copy buffer to device, one page at a time.mov dptr, #0 ; initialize address pointerx62:mov addr_lo, dpl ; set up addressmov addr_hi, dph ;mov kount, #PSIZE ; bytes per pagemov b, #120 ; retry counterx63:mov a, #PADDR ; programmable addresscall write_block ; try to writejnc x64 ; jump if write OKdjnz b, x63 ; try againsetb c ; set timeout error flagjmp x66 ; exitx64:; Add page size to address pointer.mov a, dpl ; get low byteadd a, #PSIZE ; add page sizemov dpl, a ; save low bytejnc x65 ; jump if high byte not affectedinc dph ; increment high bytex65:; cjne a, #(LOW SIZE), x62 ; jump if low byte not lastmov a, dph ; check high bytecjne a, #(HIGH SIZE), x62 ; jump if not lastclr c ; 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.mov dptr, #0 ; initialize address pointerx71:mov addr_lo, dpl ; set up addressmov addr_hi, dph ;mov kount, #PSIZE ; bytes per pagemov b, #120 ; retry counterx72:mov a, #PADDR ; programmable addresscall read_block ; try to readjnc x74 ; jump if read OKdjnz b, x72 ; try againx73:setb c ; set error flagjmp x77 ; exitx74:; Verify buffer contents.mov b, #PSIZE ; bytes per pagemov index, #buffer ; point to bufferx75:cjne @index, #FILL, x73 ; jump if compare failsinc index ; advance pointerdjnz b, x75 ; next byte; Add page size to address pointer.mov a, dpl ; get low byteadd a, #PSIZE ; add page sizemov dpl, a ; save low bytejnc x76 ; jump if high byte not affectedinc dph ; increment high bytex76:; cjne a, #(LOW SIZE), x71 ; jump if low byte not last mov a, dph ; check high bytecjne a, #(HIGH SIZE), x71 ; jump if not lastclr c ; 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.call startjc x38 ; abort if bus not availablerl a ; programmable address to bits 3:1orl a, #FADDR ; add fixed addressclr acc.0 ; specify write operationcall shout ; send device addressjc x37 ; abort if no acknowledgemov a, addr_hi ; send high byte of addresscall shout ;jc x37 ; abort if no acknowledgemov a, addr_lo ; send low byte of addresscall shout ;jc x37 ; abort if no acknowledgemov index, #buffer ; point to bufferx36:mov a, @index ; get datacall shout ; send datajc x37 ; abort if no acknowledgeinc index ; advance buffer pointerdjnz kount, x36 ; next byteclr c ; clear error flagx37:call stopx38: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.call startjc x35 ; abort if bus not availablerl a ; programmable address to bits 3:1orl a, #FADDR ; add fixed addressmov index, a ; save copy of device address clr acc.0 ; specify write operationcall shout ; send device addressjc x34 ; abort if no acknowledgemov a, addr_hi ; send high byte of address call shout ;jc x34 ; abort if no acknowledgemov a, addr_lo ; send low byte of address call shout ;jc x34 ; abort if no acknowledge; Send read command and receive data.call start ; second start for readjc x34 ; abort if bus not availablemov a, index ; get device addresssetb acc.0 ; specify read operationcall shout ; send device addressjc x34 ; abort if no acknowledgemov index, #buffer ; point to bufferx31:call shin ; receive data bytemov @index, a ; save datacjne kount, #1, x32 ; jump if not last byte call NAK ; do not acknowledge last bytejmp x33 ; donex32:call ACK ; acknowledge byteinc index ; advance buffer pointerdjnz kount, x31 ; next bytex33:clr c ; clear error flagx34:call stopx35: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.call startjc x49 ; abort if bus not availablerl a ; programmable address to bits 3:1orl a, #FADDR ; add fixed addressclr acc.0 ; specify write operationcall shout ; send device addressjc x48 ; abort if no acknowledgemov a, addr_hi ; send high byte of addresscall shout ;jc x48 ; abort if no acknowledgemov a, addr_lo ; send low byte of addresscall shout ;jc x48 ; abort if no acknowledgemov a, zdata ; get datacall shout ; send datajc x48 ; abort if no acknowledgeclr c ; clear error flagx48:call stopx49: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.call startjc x45 ; abort if bus not availablerl a ; programmable address to bits 3:1orl a, #FADDR ; add fixed addresssetb acc.0 ; specify read operationcall shout ; send device addressjc x44 ; abort if no acknowledgecall shin ; receive data bytecall NAK ; do not acknowledge byteclr c ; clear error flagx44:call stopx45: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.push bmov b, a ; save copy of programmable address; Send dummy write command to set internal address.call startjc x47 ; abort if bus not availablerl a ; programmable address to bits 3:1orl a, #FADDR ; add fixed addressclr acc.0 ; specify write operationcall shout ; send device addressjc x46 ; abort if no acknowledgemov a, addr_hi ; send high byte of addresscall shout ;jc x46 ; abort if no acknowledgemov a, addr_lo ; send low byte of addresscall shout ;jc x46 ; abort if no acknowledge; Call Current Address Read function.mov a, b ; get programmable addresscall read_currentjmp x47 ; exitx46:call stopx47:pop bretstart:; Send START, defined as high-to-low SDA with SCL high. ; Return with SCL, SDA low.; Returns CY set if bus is not available.setb SDAsetb SCL; Verify bus available.jnb SDA, x40 ; jump if not highjnb SCL, x40 ; jump if not highnop ; enforce setup delay and cycle delayclr SDAnop ; enforce hold delaynop ;nop ;nop ;nop ;clr SCLclr c ; clear error flagjmp x41x40:setb c ; 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. clr SDAnop ; enforce SCL low and data setupnopsetb SCLnop ; enforce setup delaynop ;nop ;nop ;nop ;setb SDAretshout:; Shift out a byte to the AT24Cxx, most significant bit first. ; SCL, SDA expected low on entry. Return with SCL low.; Called with data to send in A.; Returns CY set to indicate failure by slave to acknowledge. ; Destroys A.push bmov b, #8 ; bit counterx42:rlc a ; move bit into CYmov SDA, c ; output bitnop ; enforce SCL low and data setupsetb SCL ; raise clocknop ; enforce SCL highnop ;nop ;nop ;clr SCL ; drop clockdjnz b, x42 ; next bitsetb SDA ; release SDA for ACKnop ; enforce SCL low and tAAnop ;setb SCL ; raise ACK clocknop ; enforce SCL highnop ;nop ;nop ;mov c, SDA ; get ACK bitclr SCL ; drop ACK clockpop bretshin:; Shift in a byte from the AT24Cxx, most significant bit first. ; SCL expected low on entry. Return with SCL low.; Returns received data byte in A.setb SDA ; make SDA an inputpush bmov b, #8 ; bit countx43:nop ; enforce SCL low and data setupnop ;nop ;setb SCL ; raise clocknop ; enforce SCL highnop ;mov c, SDA ; input bitrlc a ; move bit into byteclr SCL ; drop clockdjnz b, x43 ; next bitpop bretACK:; Clock out an acknowledge bit (low).; SCL expected low on entry. Return with SCL, SDA low.clr SDA ; ACK bitnop ; enforce SCL low and data setupnop ;setb SCL ; raise clocknop ; enforce SCL highnop ;nop ;nop ;clr SCL ; drop clockretNAK:; Clock out a negative acknowledge bit (high).; SCL expected low on entry. Return with SCL low, SDA high. setb SDA ; NAK bitnop ; enforce SCL low and data setupnop ;setb SCL ; raise clocknop ; enforce SCL high nop ;nop ;nop ;clr SCL ; drop clockretEND。