AVR單片機Atmega128外擴RAM
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void writeram(unsigned int iaddr, unsigned char ctemp)
{
//unsigned char caddl,caddh;
unsigned char cdatatemp=0;
RDH;
WRH;
ALEH;
DDRA = 0xFF;
DDRC = 0xFF;
PORTC=iaddr>>8;
PORTA=(unsigned char)iaddr;
ALEL;//鎖存A0-A7
WRL;
PORTA=ctemp;
asm("nop;");
WRH;
ALEH;
return;
}
#endif
#define RAMSTARTADDR 0X1100
#define RAMENDADDR 0X90FF
#define RAMLEN 32768
// 測試32KRAM 用的是UT62256和74HC573
int main(void)
{
unsigned int k=0;
unsigned int i=0,j=0;
unsigned char DATA,u;
init_devices();
MCUCR = 0x80; // 允許外部并行擴展接口
XMCRA = 0x00; //0x00 external memory
XMCRB = 0x01; // 釋放PC7，作為通用I/O引腳使用
DDRC = 0xff; // PC7,PC6用于輸出，（不影響PC0-PC6地址線）
PORTC = 0x00; // PC7,PC6輸出0，（不影響PC0-PC6地址線）
//由于是32KB所以PC7用作62256片選使能，可以釋放P7為普通IO使用，輸出低電平使能62256
sendstring1("init system ok!");
sendstring1("now test system-ram all is 32k !");
sendstring1("----now write ram");
_delay_ms(1300);
#if 1
for(i=0;i32768;i++)
{
if(i%2)
*(p+i)=(unsigned char)(p+i);
else
*(p+i)=0xff;
_delay_us(10);
}
// #else
sendstring1("----write ok");
sendstring1("----now check write");
sendstring1("----now read ram");
for(i=0;i32768;i++)
{
DATA = *(p+i);
sendstring1("addr=");
sendinthex1((unsigned int)(p+i));
sendstring1("=");
sendinthex1(DATA);
sendstring1("");
}
#endif
sendstring1("---- test system-ram end!");
}
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