Bitfields for AMD-645 PCI IRQ Edge/Level Select register:
Bit(s)	Description	)
 7-4	reserved
 3	PIRQA# is edge-sensitive rather than level-sensitive
 2	PIRQB# is edge-sensitive
 1	PIRQC# is edge-sensitive
 0	PIRQD# is edge-sensitive
SeeAlso: #01011,#01023,#01025