 |
|
| If you can't view the Datasheet, Please click here to try to view without PDF Reader . |
|
|
|
| If you can't view the Datasheet, Please click here to try to view without PDF Reader . |
|
|
| Datasheet File OCR Text: |
| Application Note by Applications Staff This application note demonstrates how the Xicor X24129 Serial EEPROM can be interfaced to the 68HC11 microcontroller family when connected as shown in Figure 1. The interface uses two general AN 105 Interfacing the 400KHz X24129 Serial EEPROM to the Motorola 68HC11 Microcontroller purpose port D pins to interface to the serial memory. The 68HC11 assembly code listing for this application note can be obtained from the Xicor website at http:// www.xicor.com Figure 1. Typical hardware connection for interfacing an X24129EEPROM to the 68HC11 microcontroller. October, 2000 www.xicor.com 1 of 14 Application Note ******************************************************************************* ** ** DESCRIPTION: ** ** This file contains general utility routines written in 68HC11 assembly ** language used to interface the M68HC11 to the XICOR Two-wire X24129 ** Serial E2PROM. The interface between the 68HC11 and X24129 device ** consists of a clock (SCL) and a bidirectional data line (SDA). The ** communication interface uses 2 pins from Port D(PD3 = SCL and PD2 = SDA). ** Other components may reside on this bus provided that they do not have the ** same device identifier byte as the Serial E2PROM. ** The following table lists all the subroutines in this file with a brief ** description: ** ** START: Generate the start condition ** STOP: Generate the stop condition ** RESET: Issues the appropriate commands to force device reset ** ProgPage: Transfer from RAM buffer to serial memory page ** ProgByte: Transfer from RAM buffer to serial memory byte ** SeqRead: Read multiple bytes, starting from current address pointer ** RandomRead: Read a byte from a specific memory location ** ACKPoll: Return when the write cycle completes. ** OutACK: Process the acknowledge output cycle ** GetACK: process the acknowledge from the slave device ** ** The Main program loop programs a test string into the Serial E2PROM. After ** entire string is programmed, the content of the programmed page is read. ** The read data is stored in the internal RAM. A utility program can be ** written to verify that the buffer content matches the test string. ** ******************************************************************************* ******************************************************************************* * INTERNAL RAM ******************************************************************************* RAMBASE RAMBuff STACK EQU EQU EQU $0000 THE INTERNAL RAM BASE ADDRESS(Default) RAMBASE RAM BUFFER ADDRESS RAMBASE+$FF ******************************************************************************* * PROGRAM CONSTANTS ******************************************************************************* DWOM SDAbit SCLbit PageNO BLX WEL RWEL WPEN WELon RWELon EQU EQU EQU EQU EQU EQU EQU EQU EQU EQU $20 $04 $08 $00 $18 $02 $04 $80 00000010b 00000110b PORT D WOM CONTROL BIT PORT D BITS FUNCTIONING AS BIDIRECTIONAL SERIAL DATA (SDA) AND SERIAL CLOCK (SCL) PAGE NUMBER OF THE SERIAL MEMORY BLX BITs POSITION IN WPR WEL BIT POSITION IN WPR RWEL BIT POSITION IN WPR WPEN BIT POSITION IN WPR WEL CONTROL BYTE RWEL CONTROL BYTE October, 2000 www.xicor.com 2 of 14 Application Note MaxDelay EQU SeqReadSize EQU $1000 16 NUMBER OF TIMES TO CHECK ACKNOWLEDGE POLLING BYTE COUNTS TO SHIFT OUT USING SEQ READ DeviceID HiADDRmask WPR_ADDR PageSize EQU EQU EQU EQU $50 $3F $FFFF 32 DEVICE SELECT SHIFTED ONE BIT TO THE RIGHT MASK FOR UPPER ADDRESS BYTE WPR PHYSICAL ADDRESS LOCATION (BYTE ACCESS) BYTES PER PAGE ******************************************************************************* * INTERNAL REGISTERS AND CONTROL BLOCK ******************************************************************************* PORTD DDRD SPCR EQU EQU EQU $08 $09 $28 PORT D DATA REGISTER DATA DIRECTION REGISTER FOR PORT D SPI CONTROL REGISTER ******************************************************************************* * RESET VECTOR ENTRY POINT ******************************************************************************* ORG FDB $FFFE $E000 RESET VECTOR ADDRESS TO PROGRAM ENTRY JUMP TO BEGINNING OF EXECUTABLE CODE * ASSEMBLER REQUIREMENT- CPU TYPE P68H11 ******************************************************************************* * START OF USER CODE * ******************************************************************************* ORG $E000 MAIN: lds #STACK * LOAD STACK POINTER * INITIALIZE THE BUFFER BEFORE PROGRAMMING THE CONTENT TO A PAGE ldy ldx InitRAM: ldaa staa iny inx tsta bne ldx bset ldaa staa ldaa #RAMBuff #TestString 0,x 0,y * IY = RAM BUFFER ADDRESS * IX = TEST STRING ADDRESS * COPY THE TEST STRING TO * RAM BUFFER InitRAM #$1000 SPCR,X,#DWOM #$0C DDRD,X #$FF * * * * * SET REGISTER BASE CONFIG. PORT-D AS OPEN DRAIN PD2 = SCL PD3 = SDA CONFIGURE PORT D October, 2000 www.xicor.com 3 of 14 Application Note staa jsr PORTD,X Reset * RESET THE INTERFACE STATE MACHINE ldd #WPR_ADDR * READ THE WPR CONTENT AND FIND THE jsr RandomRead * BLOCKS THAT ARE LOCKED. IF BOTH bita #WPEN * WPEN BIT AND WP PIN ARE HIGH THEN bne WPEN_OFF * BLx BITS ARE PROTECTED (WRITES ARE * ... WARNING ... * PERMITTED WHEN WP IS BROUGHT LOW). * MAKE SURE THAT WP PIN IS LOW BEFORE ATTEMPTING TO WRITE NEW VALUE TO * THE WPR WHEN WPEN BIT IS SET. WPEN_OFF: bita #BLX * SKIP IF THE BLx BITS ARE beq NO_BLX * CLEAR (NO BLOCKS ARE PROTECTED) clra * CLEAR THE BLOCK LOCK BITS (UNPROTECT jsr ProgBL * THE ENTIRE DEVICE), WAIT FOR jsr ACKPoll * WRITE OPERATION TO COMPLETE NO_BLX: jsr SetWEL * SET THE WRITE ENABLE BIT ldd #WPR_ADDR * READ THE WPR CONTENT AND jsr RandomRead * CHECK THAT WEL BIT bita #WEL * IS SET HIGH bne WRITES_EN * ELSE ITS A FAILURE bra * * CHECK THE DEVICE/CONNECTIONS*STOP* WRITES_EN: ldd #PageNO * D = PAGE NUMBER OF THE SERIAL MEMORY ldy #RAMBuff * IY = RAM BUFFER ADDRESS jsr ProgPage * TRANSFER BUFFER CONTENT TO THE PAGE jsr ACKPoll * WAIT TILL COMPLETION OF PAGE PROG. ldy #RAMBuff * IY = RAM BUFFER ADDRESS ldaa #$58 * LOAD THE DATE TO BE WRITTEN IN THE Y staa 0,Y * REGISTER, ASCII 'X' ldd #PageNO * LOAD THE ADDRESS TO THE ACCUM jsr ProgByte * TRANSFER BUFFER CONTENT TO THE BYTE jsr ACKPoll * WAIT TILL COMPLETION OF BYTE PROG. jsr ClrWEL * RESET THE WRITE ENABLE BIT ldd #PageNO * D = PAGE NUMBER OF THE SERIAL MEMORY ldy #RAMBuff * IY = RAM BUFFER ADDRESS jsr RandomRead * SETUP THE ADDRESS POINTER AND READ staa 0,Y * FIRST BYTE, SAVE IT TO THE BUFFER iny * ADJUST THE RAM BUFFER POINTER ldaa #.HIGH.PageNO * LOAD THE UPPER BYTE OF ADDRESS ldab #$20 * SPECIFY BYTE COUNT FOR SEQ. READ OP jsr SeqRead * READ/STORE THE REMAINING DATA bra * * END OF MAIN ******************************************************************************* *** Name: SeqRead *** Description: Read sequentially from the serial memory *** Function: This subroutine extracts contents of the serial memory and stores *** them into the specified RAM buffer. The total number of bytes to *** read should be provided along with the buffer address. This *** routine assumes that the address pointer has already been *** initialized using the InByte routine. *** Calls: Start, SlavAddr, InByte, OutACK, StopRead *** Input: IY = RAM Buffer Base Address, A = High Order Address October, 2000 www.xicor.com 4 of 14 Application Note *** B = Number of bytes to read *** Output: None *** Register Usage: A, B, IY ******************************************************************************* SeqRead: jsr Start * START sec * [C=1] READ OPERATION BIT jsr SlavAddr * SEND THE SLAVE ADDRESS BYTE SeqReadNxt: jsr InByte * START READING FROM THE CURRENT ADDRESS staa 0,Y * TOTAL NUMBER OF BYTES TO READ OUT OF iny * SERIAL MEMORY decb * beq SeqReadEnd * jsr OutACK * SEND AN ACKNOWLEDGE TO THE DEVICE bra SeqReadNxt SeqReadEnd: jmp StopRead * END OF READ OPERATION ******************************************************************************* *** Name: RandomRead *** Description: Reads content of the serial memory at a specific location. *** Function: This subroutine sends out the command to read the content of a *** memory location specified in the (D) register. *** Calls: Start, InByte, SlavAddr, OutByte, StopRead *** Input: D = Address of the byte *** Output: A = Read value *** Register Usage: A ******************************************************************************* RandomRead: psha * SAVE ADDRESS TO STACK jsr Start * START clc * [C=0] WRITE OPERATION BIT jsr SlavAddr * SEND THE SLAVE ADDRESS BYTE pula * RETRIEVE ADDRESS FROM STACK jsr OutByte * LOAD THE UPPER BYTE OF THE PAGE tba * LOAD THE LOWER BYTE OF THE PAGE jsr OutByte * ADDRESS AND SHIFT OUT TO THE DEVICE jsr Start * START sec * [C=1] READ OPERATION BIT jsr SlavAddr * SEND THE SLAVE ADDRESS BYTE jsr InByte * SHIFT IN A BYTE FROM THE DEVICE jmp StopRead * END OPERATION ******************************************************************************* *** Name: StopRead *** Description: Terminate read operation *** Function: This subroutine is called at the end of a read operation. The *** routine generates the last ACK clock cycle followed by a stop *** command. The last ACK bit clock cycle differs from the normal *** ACK bit in that the SDA line is held high. This action notifies *** the serial memory that it should suspend operation. *** Calls: ClockPulse, Stop *** Input: None *** Output: None October, 2000 www.xicor.com 5 of 14 Application Note *** Register Usage: None ******************************************************************************* StopRead: bset PORTD,X,#SDAbit * MAKE SURE THAT THE DATA LINE IS HIGH bset DDRD,X,#SDAbit * CHANGE THE PDx DIRECTION TO OUTPUT jsr ClockPulse * jmp Stop * END OPERATION ******************************************************************************* *** Name: ProgPage *** Description: Update a page of the serial memory *** Function: This subroutine transfers the contents of the given buffer to the *** serial memory. The caller program must supply the page *** number of the serial memory to update and the base address *** of the RAM buffer. *** Calls: Start, SlavAddr, OutByte, Stop *** Input: IY = RAM Buffer Base Address, D(AB) = Page Number *** Output: None *** Register Usage: A,B ******************************************************************************* ProgPage: psha * SAVE ADDRESS TO THE STACK jsr Start * START clc * [C=0] WRITE OPERATION BIT jsr SlavAddr * SEND THE SLAVE ADDRESS BYTE pula * RETRIEVE ADDRESS FROM STACK jsr OutByte * LOAD THE UPPER BYTE OF THE PAGE ADDRESS tba * LOAD THE LOWER BYTE OF THE PAGE ADDRESS anda #$0E0 * MASK OUT THE UNWANTED LOWER BITS jsr OutByte * AND SHIFT OUT TO THE DEVICE ldab #PageSize * TRANSFER CONTENT OF THE RAM BUFFER ProgPageNxt: ldaa 0,Y * TO THE SERIAL MEMORY MEMORY jsr OutByte * IY SHOULD BE POINTING TO THE BUFFER ldaa #$0FF * COVER UP YOUR TRACKS AS BUFFER IS staa 0,Y * READ AND STORED TO THE SERIAL MEMORY iny * TOTAL NUMBER OF BYTES TRANSFERED decb * TO THE SERIAL MEMORY SHOULD NOT EXCEED bne ProgPageNxt * THE PAGE SIZE jmp Stop * END OF THE OPERATION ******************************************************************************* *** Name: ProgByte *** Description: Update a byte of the serial memory *** Function: This subroutine transfers a byte located in the Y register to the *** serial memory. *** Calls: Start, SlavAddr, OutByte, Stop *** Input: IY = RAM Buffer Base Address, *** Output: None *** Register Usage: A,B ******************************************************************************* ProgByte: October, 2000 www.xicor.com 6 of 14 Application Note psha jsr clc jsr pula jsr tba jsr ldaa jsr jmp Start SlavAddr OutByte OutByte 0,Y OutByte Stop * * * * * * * * * * * SAVE ADDRESS TO THE STACK START [C=0] WRITE OPERATION BIT SEND THE SLAVE ADDRESS BYTE RETRIEVE ADDRESS FROM STACK LOAD THE UPPER BYTE OF THE PAGE ADDRESS LOAD THE LOWER BYTE OF THE PAGE ADDRESS AND SHIFT OUT TO THE DEVICE TO THE SERIAL MEMORY MEMORY IY SHOULD BE POINTING TO THE BYTE DATA END OF THE OPERATION ******************************************************************************* *** Name: EnProgWPR *** Description: Enable updates to Write Protect Register (WPR) *** Function: This subroutine writes the appropriate sequence to the serial memory *** to enable updating of the WPR. The ProgWPEN and ProgBL routines *** must call this subroutine before writes to the WPR are allowed. *** Once this sequence is activated, the only way to exit this mode *** is by writing to the WPR or resetting the serial memory. *** Calls: RandomRead, SetWEL, SetRWEL *** Input: None *** Output: A = INITIAL WPR VALUE *** Register Usage: A, B ******************************************************************************* EnProgWPR: ldd #WPR_ADDR * READ THE WPR CONTENT AND jsr RandomRead * TEST THE STATUS OF bita #WEL * THE WEL BIT AND bne ProgWPR_1 * SKIP IF ITS SET psha * ALL WRITES TO THE WPR ARE DISALLOWED jsr SetWEL * WHEN THE WEL IS CLEAR, SEND SET WEL pula * COMMAND ProgWPR_1: bita #RWEL * CHECK THE RWEL BIT AND bne ProgWPR_2 * SKIP IF ITS SET psha * WRITING TO BLOCK-LOCK BITS OR WPEN jsr SetRWEL * BIT REQUIRE THAT RWEL TO BE SET, pula * SEND SET RWEL COMMAND ProgWPR_2: rts ******************************************************************************* *** Name: ProgBL *** Description: Update Block Lock bits in WPR of the serial memory *** Function: This subroutine writes to the WPR of the serial memory and *** changes the BL1:0. The caller program must supply the new values *** for the BL1:0 bits. This routine retains the original state of *** the WPEN bit. *** Calls: AddrWPR, EnProgWPR, OutByte, Stop *** Input: A[1:0] = BL[1:0] *** Output: None *** Register Usage: A, IY October, 2000 www.xicor.com 7 of 14 Application Note ******************************************************************************* ProgBL: anda #$03 * MASK OUT THE UNWANTED BITS asla * SHIFT THE BLx BITS TO THE asla * BIT POSITIONS 4:3 asla psha * SAVE THE BLx NEW VALUES AND jsr EnProgWPR * ENABLE WRITING TO THE WPR anda #$9A * CREATE THE DATA PATTERN BY MASKING oraa #$02 * IN THE DESIRED BIT PATTERN AND tsy * SAVING STATUS OF WPEN BIT oraa 0,y * SET THE BLx BITS PER REQUESTED PATTERN staa 0,y * SAVE THE WPR VALUE ONTO THE STACK jsr AddrWPR * GENERATE WPR WRITE COMMAND pula * SHIFT OUT WPR PATTERN jsr OutByte * TO THE DEVICE jmp Stop ******************************************************************************* *** Name: ProgWPEN *** Description: Update Write Protect Enable bit in WPR of the serial memory *** Function: This subroutine writes to the WPR of the serial memory and *** changes the WPEN bit. The caller program must supply the new *** value of the WPEN bit. The state of the BL1:0 bits are preserved. *** Calls: AddrWPR, EnProgWPR, OutByte, Stop *** Input: C *** Output: None *** Register Usage: A, IY ******************************************************************************* ProgWPEN: clra * LOAD THE STATUS FLAGS rora * MASK OUT THE UNWANTED BITS psha * SAVE THE WPEN BIT NEW VALUE AND jsr EnProgWPR * ENABLE WRITING TO THE WPR anda #$9A * CREATE THE DATA PATTERN BY MASKING oraa #$02 * IN THE DESIRED BIT PATTERN AND tsy * SAVING STATUS OF WPEN BIT oraa 0,y * SET THE WPEN BIT PER AS REQUESTED staa 0,y * SAVE THE WPR VALUE ONTO THE STACK jsr AddrWPR * GENERATE WPR WRITE COMMAND pula * SHIFT OUT WPR PATTERN jsr OutByte * TO THE DEVICE jmp Stop ******************************************************************************* *** Name: SetWEL *** Description: Set the Write Enable Latch (WEL) bit in the WPR of the serial memory. *** Function: This subroutine writes to the WPR of the serial memory and *** sets the WEL bit. *** Calls: AddrWPR, OutByte, Stop *** Input: NONE *** Output: NONE *** Register Usage: A ******************************************************************************* October, 2000 www.xicor.com 8 of 14 Application Note SetWEL: jsr ldaa jsr jmp AddrWPR #WELon OutByte Stop * GENERATE WPR WRITE COMMAND * SHIFT OUT WEL-ON PATTERN * TO THE DEVICE ******************************************************************************* *** Name: ClrWEL *** Description: Reset the Write Enable Latch (WEL) bit in the WPR of the serial memory. *** Function: This subroutine writes to the WPR of the serial memory and *** resets the WEL bit. *** Calls: AddrWPR, OutByte, Stop *** Input: NONE *** Output: NONE *** Register Usage: A ******************************************************************************* ClrWEL: jsr AddrWPR * GENERATE WPR WRITE COMMAND clra * SHIFT OUT WEL-OFF PATTERN jsr OutByte * TO THE DEVICE jmp Stop ******************************************************************************* *** Name: SetRWEL *** Description: Set Register Write Enable Latch bit in the WPR of the serial memory. *** Function: This subroutine writes to the WPR of the serial memory and *** sets the RWEL bit. *** Calls: AddrWPR, OutByte, Stop *** Input: NONE *** Output: NONE *** Register Usage: A ******************************************************************************* SetRWEL: jsr AddrWPR * GENERATE WPR WRITE COMMAND ldaa #RWELon * SHIFT OUT RWEL-ON PATTERN jsr OutByte * TO THE DEVICE jmp Stop ******************************************************************************* *** Name: AddrWPR *** Description: Initiate write operation to the WPR of the serial memory. *** Function: This subroutine issues the WPR address and write instruction *** to the serial memory. *** Calls: Start, SlavAddr, OutByte *** Input: NONE *** Output: NONE *** Register Usage: A,B ******************************************************************************* AddrWPR: ldd #WPR_ADDR psha * SAVE ADDRESS TO STACK October, 2000 www.xicor.com 9 of 14 Application Note jsr Start clc jsr SlavAddr pula jsr OutByte tba jmp OutByte * * * * * * * START [ C = OPERATION BIT ] [C=0] WRITE OPERATION BIT SEND THE SLAVE ADDRESS BYTE RETRIEVE ADDRESS FROM STACK LOAD THE UPPER BYTE OF ADDRESS LOAD THE LOWER BYTE OF ADDRESS AND SHIFT OUT TO THE DEVICE ******************************************************************************* *** Name: SlavAddr *** Description: Build the slave address for the serial memory. *** Function: This subroutine concatenates the bit fields for Device ID, *** the high address bits and the command bit. The resultant *** byte is then transmitted to the serial memory. *** Calls: OutByte *** Input: D(AB) = Page number *** C = COMMAND BIT (=0 WRITE, =1 READ) *** Output: None *** Register Usage: A ******************************************************************************* SlavAddr: ldaa #$50 * LOAD DEVICEID INTO ACCUM rola * MERGE THE COMMAND BIT jmp OutByte * SEND THE SLAVE ADDRESS ******************************************************************************* *** Name: OutByte *** Description: Sends a byte to the serial memory *** Function: This subroutine shifts out a byte, MSB first, through the *** assigned SDA/SCL lines on port D. *** Calls: ClockPulse, GetACK *** Input: A = Byte to be sent *** Return Value: None *** Register Usage: A ******************************************************************************* OutByte: bset DDRD,X,#SDAbit sec OutByteNxt: rola bcc OutByte0 bset PORTD,X,#SDAbit bra OutByte1 OutByte0: bclr PORTD,X,#SDAbit OutByte1: jsR ClockPulse cmpa #10000000b clc bne OutByteNxt jmp GetACK * CHANGE THE PDx DIRECTION TO OUTPUT * SHIFT OUT THE BYTE, MSB FIRST * * * * * CLOCK THE DATA INTO THE SERIAL MEMORY MEMORY LOOP IF ALL THE BITS HAVE NOT BEEN SHIFTED OUT CHECK FOR AN ACK FROM THE DEVICE October, 2000 www.xicor.com 10 of 14 Application Note ******************************************************************************* *** Name: InByte *** Description: Shifts in a byte from the serial memory *** Function: This subroutine shifts in a byte, MSB first, through the *** assigned SDA/SCL lines on port D. After the byte is received *** this subroutine does not send out an ACK bit to the serial memory. *** Calls: ClockPulse *** Input: None *** Return Value: A = Received byte *** Register Usage: A ******************************************************************************* InByte: ldaa #00000001b bclr DDRD,X,#SDAbit * CHANGE THE PDx DIRECTION TO INPUT InByteNxt: jsr ClockPulse * CLOCK THE SERIAL MEMORY MEMORY AND SHIFT rola * INTO ACC. THE LOGIC LEVEL ON THE SDA bcc InByteNxt * LINE. THE DEVICE OUTPUTS DATA ON SDA, rts * MSB FIRST ******************************************************************************* *** Name: ClockPulse *** Description: Generate a clock pulse *** Function: This subroutine forces a high-low transition on the *** assigned SCL line on port D. It also samples the SDA *** line state during high clock period. *** Calls: None *** Input: None *** Return Value: C = SDA line status *** Register Usage: None ******************************************************************************* ClockPulse: bset PORTD,X,#SCLbit * FORCE SCL LINE HIGH. BASED nop * ON AN 8MHz CRYSTAL FREQ. THE SYSTEM nop clc * BUS CYCLE TIME IS 0.5 MICROSEC. brclr PORTD,X,#SDAbit,ClockPulseLo * sec ClockPulseLo: bclr PORTD,X,#SCLbit * LOWER THE CLOCK LINE rts ******************************************************************************* *** Name: OutACK *** Description: Send out an ACK bit to the serial memory *** Function: This subroutine changes the direction of the SDA pin on port D *** and then clocks an ACK bit to the serial memory. The ACK *** cycle acknowledges a properly received data by lowering the *** SDA line during this period (9th clock cycle of a received *** byte). The direction of the SDA pin is programmed as input *** prior to returning to the caller. *** Calls: ClockPulse *** Input: None October, 2000 www.xicor.com 11 of 14 Application Note *** Return Value: None *** Register Usage: None ******************************************************************************* OutACK: bclr PORTD,X,#SDAbit * MAKE SURE THAT THE DATA LINE IS LOW bset DDRD,X,#SDAbit * CHANGE THE PDx DIRECTION TO OUTPUT jmp ClockPulse * ******************************************************************************* *** Name: GetACK *** Description: Clock the serial memory for an ACK cycle *** Function: This subroutine changes the direction of the SDA pin on port D *** and then clocks the serial memory. It returnes the sampled *** logic level on the SDA during high clock cycle. The serial memory *** acknowledges a properly received command/data by lowering the *** SDA line during this period (9th clock cycle of a transmitted *** byte). If the SDA state is HIGH, it signifies that either it *** did not receive the correct number of clocks or it's stuck in *** previously initiated write command, *** Calls: ClockPulse *** Input: None *** Return Value: C = ACKnowledge bit *** Register Usage: None ******************************************************************************* GetACK: bclr DDRD,X,#SDAbit * CHANGE THE PDx DIRECTION TO INPUT jsr ClockPulse * CLOCK THE SERIAL MEMORY bset DDRD,X,#SDAbit * CHANGE THE PDx DIRECTION TO OUTPUT rts ******************************************************************************* *** Name: ACKPoll *** Description: Wait for an ACK from the serial memory *** Function: This subroutine sends a slave address to the serial memory and *** monitors the SDA for an ACK signal. It returns if a low *** logic level is detected on the SDA during high clock cycle of *** the acknowledge cycle. The serial memory does not respond to any *** commands with an acknowledge bit while the store operation *** is in progress. If no ACK is received another slave address is *** sent to the serial memory. The number of iteration is specified *** by the MaxDelay constant. *** Calls: Start, SlavAddr, Stop *** Input: None *** Return Value: C = ACKnowledge bit [=0 ACK ,=1 No ACK was received] *** Register Usage: A, B, IY ******************************************************************************* ACKPoll: ldy #MaxDelay * LOAD MAX NO. OF ACK POLLING CYCLE ACKPollnxt: jsr Start * START THE ACK POLL CYCLE AND ldd #PageNO * D = PAGE NUMBER OF THE SERIAL MEMORY clc * [C=0] WRITE OPERATION BIT jsr SlavAddr * SEND THE SLAVE ADDRESS. THEN October, 2000 www.xicor.com 12 of 14 Application Note jsr Stop bcc ACKPollExit dey bne ACKPollnxt ACKPollExit: rts * OPERATION BY A STOP CONDITION. * EXIT IF THE ACK WAS RECEIVED * LOOP WHILE THE MAXIMUM NO. OF CYCLES ******************************************************************************* *** Name: Start *** Description: Send a start command to the serial memory *** Function: This subroutine generates a start condition on the bus. The start *** condition is defined as a high-low transition on the SDA *** line while the SCL is high. The start is used at the beginning *** of all transactions. *** Calls: None *** Input: None *** Return Value: None *** Register Usage: None ******************************************************************************* Start: bset PORTD,X,#SDAbit * FORCE THE SDA LINE HIGH bset PORTD,X,#SCLbit * FORCE THE SCL CLOCK LINE HIGH bclr PORTD,X,#SDAbit * BEFORE TAKING THE SDA LOW nop nop nop nop bclr PORTD,X,#SCLbit * FORCE THE SCL LOW rts ******************************************************************************* *** Name: Stop *** Description: Send stop command to the serial memory *** Function: This subroutine generates a stop condition on the bus. The stop *** condition is defined as a low-high transition on the SDA *** line while the SCL is high. The stop is used to indicate end *** of current transaction. *** Calls: None *** Input: None *** Return Value: None *** Register Usage: None ******************************************************************************* Stop: bclr PORTD,X,#SDAbit * FORCE THE SDA LOW BEFORE TAKING bset PORTD,X,#SCLbit * THE SCL CLOCK LINE HIGH nop nop nop nop bset PORTD,X,#SDAbit * FORCE THE SDA HIGH (IDLE STATE) rts ******************************************************************************* *** Name: Reset October, 2000 www.xicor.com 13 of 14 Application Note *** Description: Resets the serial memory *** Function: This subroutine is written for the worst case. System interruptions *** caused by brownout or soft error conditions that reset the main *** CPU may have no effect on the internal Vcc sensor and reset *** circuit of the serial memory. These are unpredictable and *** random events that may leave the serial memory interface *** logic in an unknown state. Issuing a Stop command may not be *** sufficient to reset the serial memory. *** Calls: Start, Stop *** Input: None *** Return Value: None *** Register Usage: B ******************************************************************************* Reset: ldab #$0A * APPLY 10 CLOCKS TO THE DEVICE. EACH ResetNxt: jsr Start * CYCLE CONSISTS OF A START/STOP jsr Stop * THIS WILL TERMINATE PENDING WRITE decb * COMMAND AND PROVIDES ENOUGH CLOCKS bne ResetNxt * FOR UNSHIFTED BITS OF A READ rts * OPERATION TestString: FCC FCB $00 'xICOR MAKES IT MEMORABLE!' ******************************************************************************* *** END OF X24320/640/128 SERIAL MEMORY INTERTERFACE SOURCE CODE ******************************************************************************* END October, 2000 www.xicor.com 14 of 14 |
Price & Availability of AN105
 |
|
|
|
|
All Rights Reserved © IC-ON-LINE 2003 - 2022 |
| [Add Bookmark] [Contact Us] [Link exchange] [Privacy policy] |
|
Mirror Sites : [www.datasheet.hk]
[www.maxim4u.com] [www.ic-on-line.cn]
[www.ic-on-line.com] [www.ic-on-line.net]
[www.alldatasheet.com.cn]
[www.gdcy.com]
[www.gdcy.net] |