w83977atf Winbond Electronics Corp America, w83977atf Datasheet - Page 167

• Manufacturer Part Number: w83977atf
• Description: Winbond I/o
• Manufacturer: Winbond Electronics Corp America

W83977ATF
P EL MI AR
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
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.
After a power-on reset, the
W83977ATF
W83977ATF
enters the extended function mode, a specific value must be programmed into the Extended Function
Function Enable Registers are write-only registers. On a PC/AT system, their port addresses are
3F0h or 370h (as described in previous section).
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
Data Register (EFDR). The EFIRs are write-only registers with port address 3F0h or 370h on PC/AT
systems; the EFDRs are read/write registers with port address 3F1h or 371h on PC/AT systems.
To program W83977ATF configuration registers, the following configuration sequence must be
followed:
(2). Configure the configuration registers
(3). Exit 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).
The chip selects the logical device and activates the desired logical devices through Extended
Function Index Register(EFIR) and Extended Function Data Register(EFDR). EFIR is located at the
First, write the Logical Device Number (i.e.,0x07) to the EFIR and then write the number of the
desired logical device to the EFDR. If accessing the Chip(Global) Control Registers, this step is not
Secondly, write the address of the desired configuration register within the logical device to the EFIR
and then write (or read) the desired configuration register through EFDR.
Publication Release Date:April 1998
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