W83C553F Datasheet, PDF (102/159 Pages) Winbond – SYSTEM I/O CONTROLLER WITH PCI ARBITER

W83C553F
Electrical Specifications
Initialization Command Word 4 Register
Function:
Both interrupt controllers must have the Initialization Command Word 4 (ICW4) Register programmed
as part of their initialization sequence. At a minimum, bit 0 must be set to "1" to indicate it is operating
in an x86-based system.
Type:
Write Only
Bit Description:
Bits [7:5]:
Bit 4:
Bit 3:
Bit 2:
Bit 1:
Bit 0:
Reserved. These bits must be programmed to "000."
SFNM. Special Fully Nested Mode. This mode should normally be disabled by writing "0" to
this bit.
BUF. Buffered Mode. This bit must be programmed to "0" for the W83C553F.
MNS. Master/Slave in Buffered Mode. This bit must be programmed to "0" for the W83C553F.
AEOI. Automatic End of Interrupt. This bit should normally be programmed to "0." If
programmed to "1," Automatic End of Interrupt Mode is enabled.
UPM. Microprocessor Mode. This bit must be set to "1" to indicate the interrupt controller is
operating in an x86-based system.
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