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W83977EF-AW Datasheet(PDF) 83 Page - Winbond |
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W83977EF-AW Datasheet(HTML) 83 Page - Winbond |
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83 / 142 page  W83977EF-AW/W83977EG-AW Publication Release Date: Apr. 2006 -81- Revision 1.2 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 3F0h or 370h). Secondly, an index value (02h, 07h-FFh) must be written to the Extended Functions Index Register (I/O port address 3F0h or 370h 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 3F1h or 371h). 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. 10.1.2 Extended Functions Enable Registers (EFERs) After a power-on reset, W83977EF/EG enters the default operating mode. Before W83977EF/EG 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). 10.1.3 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 8.1.1) on PC/AT systems; the EFDRs are read/write registers with port address 3F1h or 371h (as described in section 8.1.1) on PC/AT systems. 10.2 Configuration Sequence To program W83977EF/EG configuration registers, the following configuration sequence must be followed: (1). Enter the extended function mode (2). Configure the configuration registers (3). Exit the extended function mode 10.2.1 Enter the extended function mode To place the chip into the extended function mode, two successive wrtites of 0x87 must be applied to Extended Function Enable Registers(EFERs, i.e. 3F0h or 370h). |
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