w83627sf Winbond Electronics Corp America, w83627sf Datasheet - Page 97

• Manufacturer Part Number: w83627sf
• Description: Winbond I/o
• Manufacturer: Winbond Electronics Corp America

W83627SF
PRELIMINARY
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.
9.1.2 Extended Functions Enable Registers (EFERs)
After a power-on reset, the W83627SF enters the default operating mode. Before the W83627SF 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 2Eh or 4Eh (as
described in previous section).
9.1.3 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 2Eh or 4Eh (as described in
section 12.2.1) on PC/AT systems; the EFDRs are read/write registers with port address 2Fh or 4Fh (as
described in section 9.2.1) on PC/AT systems.
9.2 Configuration Sequence
To program W83627SF 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
9.2.1 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. 2Eh or 4Eh).
Publication Release Date: Nov. 2000
- 90 -
Revision 0.60