W83627THF_06 Datasheet, PDF (80/142 Pages) Winbond – Winbond LPC I/O

W83627THF/W83627THG
6. PLUG AND PLAY CONFIGURATION
The W83627THF uses Compatible PNP protocol to access configuration registers for setting up
different types of configurations. In W83627THF, there are eleven Logical Devices (from Logical
Device 0 to Logical Device B with the exception of logical device 4 for backward compatibility) which
correspond to eleven individual functions: FDC (logical device 0), PRT (logical device 1), UART1
(logical device 2), UART2 (logical device 3), KBC (logical device 5), GPIO,5 (logical device 7), GPIO2
(logical device 8), GPIO3,4 (logical device 9), ACPI ((logical device A), and hardware monitor (logical
device B). 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.
6.1 Compatible PnP
6.1.1 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 2Eh twice
write 87h to the location 4Eh twice
After Power-on reset, the value on RTSA# (pin 43) is latched by HEFRAS of CR26. In Compatible
PnP, a specific value (87h) must be written twice to the Extended Functions Enable Register (I/O port
address 2Eh or 4Eh). Secondly, an index value (02h, 07h-FFh) must be written to the Extended
Functions Index Register (I/O port address 2Eh or 4Eh same as Extended Functions Enable Register)
to identify which configuration register is to be accessed. The designer can then access the desired
configuration register through the Extended Functions Data Register (I/O port address 2Fh or 4Fh).
After programming of the configuration register is finished, an additional value (AAh) should be written
to EFERs to exit the Extended Function mode to prevent unintentional access to those configuration
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Publication Release Date: September 26, 2006
Revision 1.2