// AT24C64 support functions using ATMEGA's TWI
// pin-WP is hard-wired to GND
// fuctions work better outside interrupt routines
// by MXH, 2003/07/30

＃i nclude "DStruct.h"
＃i nclude

// CONSTANTS DEFINITION FOR EEPROM
#define EEADDR?0
#define EEWR?0
#define EERD?1
// TWINT *NOT* set after STOP condition is sent
// check status?
// TWSTO is cleared by hardware
#define TwiStop()?TWCR = _BV(TWINT) | _BV(TWEN) | _BV(TWSTO)
#define TwiStart()?TWCR = _BV(TWINT) | _BV(TWEN) | _BV(TWSTA)
#define TWI_STATUS?(TWSR & 0xF8)

BYTE byEEWait;

//////////////////////////////////////////////////////////////////////////
// implementation

BOOL EEPStart(BYTE addr, BOOL bWrite)
{
byEEWait = 10;?// 90~100ms
poll_ack:
TwiStart();
while (!(TWCR & (1<if ( byEEWait == 0 ){
return FALSE;
}
}
if ((TWI_STATUS != TW_START)&&(TWI_STATUS != TW_REP_START))
goto poll_ack;
//byEEWait = 3;?// 20~30ms
// send SLA+R/W
TWDR = addr | bWrite;
TWCR = (1<while (!(TWCR & (1<if( byEEWait == 0 ){
TwiStop();
return FALSE;
}
}
if( EEWR == bWrite ){?// MT mode
//if(TWI_STATUS != TW_MT_SLA_ACK)
switch(TWI_STATUS){
case TW_MT_SLA_ACK:
break;
case TW_MT_SLA_NACK:
goto poll_ack;
default:
TwiStop();
return FALSE;
}
}else{?// MR mode
if(TWI_STATUS != TW_MR_SLA_ACK)
return FALSE;
}
return TRUE;
}

//////////////////////////////////////////////////////////////////////
//
BYTE EEPWrite( WORD uiAddress, WORD uiLen, void *pBuf ) //using 0
{
unsigned int i,j,uiCnt;

if( uiLen == 0 ) return 0;
uiCnt = 0;
//?uiEnd = uiAddress + uiLen;
i = uiAddress;
do{
if(!EEPStart(0xA0|EEADDR,EEWR)){?//PollAck() is built-in
return 0;
}
TWDR = (BYTE)((i>>8)&0x00ff);?// MSB of address
TWCR = (1<byEEWait = 3;?// 20~30ms
while (!(TWCR & (1<if( byEEWait == 0 )
return FALSE;
}
if(TWI_STATUS != TW_MT_DATA_ACK){
return FALSE;
}
TWDR = (BYTE)(i&0x00ff);?// LSB of address
TWCR = (1<byEEWait = 3;?// 20~30ms
while (!(TWCR & (1<if( byEEWait == 0 )
return FALSE;
}
if(TWI_STATUS != TW_MT_DATA_ACK)
return FALSE;
// write data
for( j=0; j<32; j++ ){
TWDR = ((BYTE*)pBuf)[uiCnt];
TWCR = (1<byEEWait = 3;?// 20~30ms
while (!(TWCR & (1<if( byEEWait == 0 )
return FALSE;
}
if(TWI_STATUS != TW_MT_DATA_ACK){
return FALSE;
}
i++;
uiCnt++;
if(( 0 == i%32 )||( uiCnt == uiLen )){
TwiStop();
break;
}
}
}while( uiCnt < uiLen );
//?while( !PollAck());
return 1;
}

//////////////////////////////////////////////////////////////////////
//
BYTE EEPRead( WORD uiAddress, WORD uiLen, void *pBuf ）
{
UINT i;

if ( uiLen == 0 ) return 0;
if(!EEPStart(0xA0|EEADDR,EEWR)){?//PollAck() is built-in
return 0;?//↑
}?// not RD but write device address to the chip
TWDR = (BYTE)(( uiAddress >> 8) & 0x00ff );?//((BYTE*)(&uiAddress))[1];?// MSB of address
TWCR = (1<byEEWait = 3;?// 20~30ms
while (!(TWCR & (1<if( byEEWait == 0 )
return FALSE;
}
if (TWI_STATUS != TW_MT_DATA_ACK)
return FALSE;
TWDR = (BYTE)( uiAddress & 0x00ff );?//((BYTE*)(&uiAddress))[0];?// LSB of address
TWCR = (1<byEEWait = 3;?// 20~30ms
while (!(TWCR & (1<if( byEEWait == 0 )
return FALSE;
}
if (TWI_STATUS != TW_MT_DATA_ACK)
return FALSE;
if(!EEPStart(0xA0+EEADDR,EERD)){?//PollAck()){
return 0;?//↑
}// ??? how to read?
for ( i=0; iTWCR = _BV(TWINT)|_BV(TWEN)|_BV(TWEA);
byEEWait = 3;?// 20~30ms
while (!(TWCR & (1<if( byEEWait == 0 )
return FALSE;
}
if (TWI_STATUS != TW_MR_DATA_ACK)
return FALSE;
((BYTE*)pBuf)[i] = TWDR;?// EEInByte();
}
TWCR = _BV(TWINT) | _BV(TWEN);?// send NACK to indicate final byte
byEEWait = 3;?// 20~30ms
while (!(TWCR & (1<if( byEEWait == 0 )
return FALSE;
}
//if (TWI_STATUS != TW_MR_DATA_ACK)
//?return FALSE;
((BYTE*)pBuf)[i] = TWDR;
TwiStop();
return 1;
}

附錄：
;============================
;STC89C51讀寫AT24C64匯編程序
;===========================
BITCNT??? EQU?????? 42H
SDADR???? EQU?????? 40H
SDA?????? BIT???????? P0.1
SCL?????? BIT???????? P0.0
ORG?????? 0000H
JMP??????? MAIN
ORG?????? 0100H

MAIN:
MOV????? R7,? #01010101B
ACALL?? WRITE_AT24C64
ACALL?? DELAY
ACALL?? READ_AT24C64
MOV????? P3,? A
ACALL?? DELAY
…
;ACALL? 顯示、鍵盤子程序
…
JMP??????? MAIN????
;=============================
DELAY:
MOV?????? R6,? #0FFH

DELAY0:
MOV?????? R5,? #0FFH

DELAY1:??????????????
DJNZ????? R5,? DELAY1
DJNZ????? R6,? DELAY0
RET
;=============================

WRITE_AT24C64:
ACALL?????????? START???????????????????? ;發送起始條件
MOV????????????? A,??? #0A0H????????????? ;AT24C64總線地址
ACALL?????????? SENTBYTE????????????????? ;發送AT24C64器件總線地址
JB????????????? F0,? SENDRETURN?????????? ;出錯返回
MOV???????????? R0,? #SDADR?????????????? ;取存儲地址
MOV???????????? A,??? @R0
ACALL?????????? SENTBYTE
JB????????????? F0,? SENDRETURN
INC???????????? R0
MOV???????????? A,??? @R0
ACALL?????????? SENTBYTE
JB????????????? F0,? SENDRETURN
MOV???????????? A,??? R7
ACALL?????????? SENTBYTE?????????????????? ;發送一次數據
JB????????????? F0,? SENDRETURN??????????? ;出錯返回
ACALL?????????? STOP?????????????????????? ;發送停止條件

DELAY10:?????
MOV???????????? R4,? #30H????????????????? ;延時10mS等待數據寫完

DELAY11:
MOV???????????? R3,? #34H
DJNZ??????????? R3,? $
DJNZ??????????? R4,??????? DELAY11

SENDRETURN:
RET
;=============================
READ_AT24C64:???????????????????????????? ;讀AT24C64
ACALL?????????? START???????????????????? ;發送IC總線起始條件
MOV???????????? A,??? #0A0H
ACALL?????????? SENTBYTE????????????????? ;AT24C64總線地址
JB????????????? F0,? RCVRETURN???? 　　?? ;出錯返回
MOV???????????? R0,? #SDADR??????????? 　 ;取存儲地址
MOV???????????? A,??? @R0
ACALL?????????? SENTBYTE????????????????? ;發送AT24C64器件總線地址
JB????????????? F0,? SENDRETURN???? 　　? ;出錯返回
INC???????????? R0
MOV???????????? A,??? @R0
ACALL?????????? SENTBYTE????????????????? ;發送AT24C64器件總線地址
JB????????????? F0,? SENDRETURN
ACALL?????????? START???????????????????? ;發送IC總線重復起始條件
MOV????????????? A,??? #0A0H????????????? ;AT24C64總線地址
SETB??????????? ACC.0???????????????? 　? ;取總線讀操作數
ACALL?????????? SENTBYTE????????????????? ;發送被控制總線地址
JB????????????? F0,? RCVRETURN?????? 　　 ;出錯返回
ACALL?????????? RCVBYTE?????????????????? ;接收數據

RCVRETURN:
RET
;===============================
START:
SETB??????????? SDA??????????? ;發送起始條件的數據信號
NOP
SETB??????????? SCL??????????? ;發送起始條件的時鐘信號
NOP
CLR???????????? SDA??????????? ;發送起始信號
NOP
CLR????????????? SCL?????????? ;準備發送或接收數據
RET
;===============================
STOP:
CLR??????? SDA????????????????? ;發送停止條件的數據信號
NOP
SETB?????? SCL????????????????? ;發送停止條件的時鐘信號
NOP
SETB?????? SDA????????????????? ;發送總線停止信號
NOP
RET
;==============================
SENTBYTE:???????????????????????? ;送數8位
MOV???????? BITCNT,#08H

SENTB:
RLC??????? A?????????? 　　??????? ;要發送的數據左移，發送入位C
MOV??????? SDA,????? C
SETB?????? SCL???????????????????? ;置時鐘線為高，通知被控制開始接
收數據位
CLR??????? SCL???????????????????? ;準備接收下一個數據位
DJNZ?????? BITCNT,SENTB??????????? ;8位沒發送完繼續發送
SETB?????? SDA???????????????????? ;8位發送完后釋放數據線準備收應答位
SETB?????? SCL???????????????????? ;開始接收應答信號
CLR??????? F0????????????????????? ;預先清發送數據出錯標志
JNB??????? SDA,????? ACKEND??????? ;判斷是否接收應答信號正常轉ACKEND
SETB?????? F0????????????????????? ;未收到應答置位錯誤標志

ACKEND:
CLR??????? SCL???????????????????? ;發送結束準備下次發送或接收數據
RET
;==============================
RCVBYTE:
SETB??????? SDA???????????????????? ;置數據線為輸入方式
MOV???????? BITCNT,#08H???????????? ;傳送的數據長度為8位

RCV:
CLR???????? SCL???????????????????? ;置時鐘線為低，準備接收數據
SETB??????? SCL???????????????????? ;置時鐘線為高使數據線上數據有效
MOV???????? C,??? SDA
RLC?????? 　A?????????????????????? ;接收的數據位放入ACC
DJNZ??????? BITCNT,RCV????????????? ;8位沒收完繼續接收
CLR??? 　?? SCL???????????????????? ;8位接收完置時鐘線和數據線
CLR?????? 　SDA
SETB??????? SDA???????????????????? ;接收非應答信號
SETB??????? SCL???????????????????? ;置時鐘線為高使應答位有效
SETB??????? SDA
CLR?????? 　SCL???????????????????? ;清時鐘線以便發送停止條件
RET
;============================
;顯示、鍵盤子程序
;===========================
END