A54SX16-2 ACTEL [Actel Corporation], A54SX16-2 Datasheet - Page 2

• Manufacturer Part Number: A54SX16-2
• Description: PCI Arbiter Core
• Manufacturer: ACTEL [Actel Corporation]

Ar bi tr at io n S che m es
Pure rotation is a turn-based method that allows each bus
master one transaction in turn if multiple masters are
requesting the bus simultaneously. If only one master
requests the bus, that master will immediately get the grant.
Figure 3
Figure 3 • Pure Rotation Arbitration
Figure 4 • Fair Rotation Arbitration
2
illustrates the pure rotation scheme.
Device 4
Device 3
Device 4
Device 3
Device 0
Device 0
IDLE
v4.0
Fair rotation is employed if an embedded processor is
required to initialize the system but will not be used after
that point. By giving it highest priority, the fair rotation
scheme allows the embedded processor access to the PCI
bus on every other transaction when it is requesting the bus
continuously. The other masters use a pure rotation scheme.
The fair rotation scheme is illustrated in
Device 1
Device 2
Device 2
Device 1
IDLE
Figure
4.