以byte方式讀取SPD的數據（SMBus Controller在PCH中）

Reading A Byte of SMBus EEPROM Data
The following steps have to be followed for the System BIOS to read a byte of the Serial Presence Detect (SPD) data from the DIMM.
1.Program the SMBus Base Address Register, D31:F3:20h.
2.Set the I/O Space enable bit, D31:F3:04h[0].
3.Set the HST_EN bit, D31:F3:40h[0].
4.Clear the status bits by programming SMBBASE 00h to 1Eh.
5.Program the SMBus Transmit Slave Address Register with the DIMM SMBus address, SMBBASE 04h. For example: If the DIMM address is A2h and a byte is to be read from the DIMM, program SMBBASE 04h to A3h (A2h OR’ed with 1 (Read/Write bit)).
6.Program the SMBus Host Command Register with the DIMM’s SPD data offset to be read, SMBBASE 03h. For example: If reading from offset 04h in the DIMM’s SPD, this register will have a value of 04h (Offset of SPD data to be read).
7.Program the SMBus Host Control Register, SMBBASE 02h[7:0] to 48h.
8.Wait on the Host Busy (HOST_BUSY) bit to be clear in the Host Status Register, SMBBASE 00h[0]. The System BIOS should use the INTR bit, SMBBASE 00h[1] and the other error indicator bits in the SMBus Host Status Register to indicate the end of the operation before reading the SMBus data register.
9.After the HOST_BUSY bit is clear, check the DEV_ERR bit in the Host Status Register, SMBBASE 00h[2] = 0, if the HOST_BUSY bit is clear and the DEV_ERR bit is clear the BIOS can read the byte value from the SMBus Data 0 Register, SMBBASE 05h.
Step #1 to Step #3 will be programmed only once. The BIOS can follow Step #4 through Step#9 multiple times to get all the necessary EEPROM data from the SMBus devices.

源码（WIN-TC编译通过）：

#include

#include

unsigned SearchBAR(unsigned long address_s)

{

unsigned long int val;

asm mov dx,0xcf8

asm db 0x66

asm mov ax,address_s

asm db 0x66

asm out dx,ax

asm mov dx,0xcfc

asm db 0x66

asm in ax,dx

asm db 0x66

asm mov val,ax

return val;

}

void WriteFlags(unsigned long pci_addr,unsigned data)

{

asm mov dx,0xcf8

asm db 0x66

asm mov ax,pci_addr

asm db 0x66

asm out dx,ax

asm mov dx,0xcfc

asm mov al,data

asm out dx,al

}

unsigned ReadByte(unsigned SMBase_addr,unsigned i)

{

unsigned val;

outportb(SMBase_addr,0x1e);

outportb(SMBase_addr 0x04,0xa7);

outportb(SMBase_addr 0x03,i);

outportb(SMBase_addr 0x02,0x48);

while((inportb(SMBase_addr))&0x01){

delay();

}

val=inportb(SMBase_addr 0x05);

return val;

}

void main()

{

unsigned long pci_addr,SMBase_addr,bus,dev,func,offset;

unsigned i,data;

bus=0x00;

dev=0x1f;

func=0x03;

pci_addr=) (dev<<) (func<<);

WriteFlags(pci_addr 0x04,0x03);

WriteFlags(pci_addr 0x40,0x11);

SMBase_addr=SearchBAR(pci_addr 0x20)&0xffe0;

printf("PCI Address:%x",pci_addr>>);

printf("%x\n",pci_addr);

printf("use IO :%x\n",SMBase_addr);

printf("Read Byte:\n");

for(i=;i<</SPAN>;i ){

data=ReadByte(SMBase_addr,i);

printf("%4x",data);

if(i%==)

printf("\n");

}

getchar();

}

转载：http://blog.sina.com.cn/s/blog_870045320102v60u.html