W83977EG-AW Datasheet, PDF (82/142 Pages) Nuvotem Talema – These products are not designed for use in life support appliances

W83977EF-AW/W83977EG-AW
10. PLUG AND PLAY CONFIGURATION
W83977EF/EG uses Compatible PNP protocol to access configuration registers for setting up different
types of configurations. In W83977EF/EG, there are nine Logical Devices (from Logical Device 0 to
Logical Device A with the exception of logical device 4 and 6 for compatibility) which correspond to
nine individual functions: FDC (logical device 0), PRT (logical device 1), UART1 (logical device 2),
UART2 (logical device 3), KBC (logical device 5), GPIO1 (logical device 7), GPIO2 (logical device 8),
and ACPI ((logical device A). Each Logical Device has its own configuration registers (above CR30).
Host can access those registers by writing an appropriate logical device number into logical device
select register at CR7.
10.1 Compatible PnP
10.1.1 Extended Function Registers
In Compatible PnP, there are two ways to enter Extended Function and read or write the configuration
registers. HEFRAS (CR26 bit 6) can be used to select one out of these two methods of entering the
Extended Function mode as follows:
HEFRAS
0
1
ADDRESS AND VALUE
write 87h to the location 3F0h twice
write 87h to the location 370h twice
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