Intel 8254x: Difference between revisions

When using MMIO, reading/writing to/from registers is very straight-forward.

 

*(uint32_t *)(ioaddr + reg) = val; // writes "val" to an MMIO address

val = *(uint32_t *)(ioaddr + reg); // reads "val" from an MMIO address

 

When using IO, reading/writing to/from registers is a little more complicated as the IO address space for the 8254x is only 8 bytes wide.

IOADDR holds the IO address that the IODATA window operates on. So, basic operation is to set the IOADDR window and then the desired action using the IODATA window.

 

outl(ioaddr + 0x00, reg); // set the IOADDR window

outl(ioaddr + 0x04, val); // write the value to the IOADDR window which will end up in the register in IOADDR

inl(ioaddr + 0x04); // read back the value

 

== Initialization ==

Obtaining the MAC is quite trivial and only requires reading the first 3-words of the EEPROM.

 

uint8_t dev_info.mac_addr[6];

 

*((uint16_t *)&dev_info.mac_addr[4]) = i8254x_read_eeprom(0x02);

i8254x_unlock_eeprom();

 

== Emulation ==