XIO2000AI TAOS [TEXAS ADVANCED OPTOELECTRONIC SOLUTIONS], XIO2000AI Datasheet - Page 99

• Manufacturer Part Number: XIO2000AI
• Description: PCI Express to PCI Bus Translation Bridge
• Manufacturer: TAOS [TEXAS ADVANCED OPTOELECTRONIC SOLUTIONS]

4.69 Arbiter Control Register
† Thes bits are reset by a PCI Express reset (PERST), a GRST, or the internally-generated power-on reset.
April 2007 Revised October 2008
BIT
7†
6†
5†
4†
3†
2†
1†
0†
The arbiter control register controls the bridge internal arbiter. The arbitration scheme used is a two-tier
rotational arbitration. The bridge is the only secondary bus master that defaults to the higher priority arbitration
tier. See Table 4−43 for a complete description of the register contents.
RESET STATE
BIT NUMBER
BRIDGE_TIER_SEL
PCI register offset:
Register type:
Default value:
FIELD NAME
TIER_SEL5
TIER_SEL4
TIER_SEL3
TIER_SEL2
TIER_SEL1
TIER_SEL0
PARK
7
0
ACCESS
Table 4−43. Arbiter Control Register Description
RW
RW
RW
RW
RW
RW
RW
RW
6
1
5
0
Bus parking mode. This bit determines where the internal arbiter parks the secondary bus.
When this bit is set, the arbiter parks the secondary bus on the bridge. When this bit is
cleared, the arbiter parks the bus on the last device mastering the secondary bus.
Bridge tier select. This bit determines in which tier the bridge is placed in the arbitration
scheme.
GNT5 tier select. This bit determines in which tier GNT5 is placed in the arbitration scheme.
GNT4 tier select. This bit determines in which tier GNT4 is placed in the arbitration scheme.
GNT3 tier select. This bit determines in which tier GNT3 is placed in the arbitration scheme.
GNT2 tier select. This bit determines in which tier GNT2 is placed in the arbitration scheme.
GNT1 tier select. This bit determines in which tier GNT1 is placed in the arbitration scheme.
GNT0 tier select. This bit determines in which tier GNT0 is placed in the arbitration scheme.
DCh
Read/Write
40h
0 = Park the secondary bus on the last secondary bus master (default)
1 = Park the secondary bus on the bridge
0 = Lowest priority tier
1 = Highest priority tier (default)
0 = Lowest priority tier
1 = Highest priority tier (default)
0 = Lowest priority tier
1 = Highest priority tier (default)
0 = Lowest priority tier
1 = Highest priority tier (default)
0 = Lowest priority tier
1 = Highest priority tier (default)
0 = Lowest priority tier
1 = Highest priority tier (default)
0 = Lowest priority tier
1 = Highest priority tier (default)
4
0
3
0
2
0
1
0
0
0
DESCRIPTION
Classic PCI Configuration Space
SCPS155C
89