W83977F-A Datasheet, PDF (127/182 Pages) Winbond – WINBOND I/O

W83977F-A/ W83977G-A/ W83977AF-A/ W83977AG-A
12.2.2 Extended Functions Enable Registers (EFERs)
After a power-on reset, the W83977F/ AF enters the default operating mode. Before the W83977F/
AF enters the extended function mode, a specific value must be programmed into the Extended
Function Enable Register (EFER) so that the extended function register can be accessed. The
Extended Function Enable Registers are write-only registers. On a PC/AT system, their port
addresses are 3F0h or 370h (as described in previous section).
12.2.3 Extended Function Index Registers (EFIRs), Extended Function Data Registers
(EFDRs)
After the extended function mode is entered, the Extended Function Index Register (EFIR) must be
loaded with an index value (02h, 07h-FEh) to access Configuration Register 0 (CR0), Configuration
Register 7 (CR07) to Configuration Register FE (CRFE), and so forth through the Extended Function
Data Register (EFDR). The EFIRs are write-only registers with port address 3F0h or 370h (as
described in section 12.2.1) on PC/AT systems; the EFDRs are read/write registers with port address
3F1h or 371h (as described in section 9.2.1) on PC/AT systems.
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Publication Release Date: May 2006
Revision 0.60