w83l517g Winbond Electronics Corp America, w83l517g Datasheet - Page 108

• Manufacturer Part Number: w83l517g
• Description: Winbond Lpc I/o For Notebook W83l517d/ W83l517d-f
• Manufacturer: Winbond Electronics Corp America

12.2 Compatible PnP
12.2.1 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:
After Power-on reset, the value on RTSA# (pin 49) 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
registers. The designer can also set bit 5 of CR26 (LOCKREG) to high to protect the configuration
registers against accidental accesses.
The configuration registers can be reset to their default or hardware settings only by a cold reset (pin
MR = 1). A warm reset will not affect the configuration registers.
HEFRAS
0
1
write 87h to the location 2Eh twice
write 87h to the location 4Eh twice
- 108 -
W83L517D/W83L517D-F
ADDRESS AND VALUE