Datasheet

5–3
5.3 Arbiter Control Register
The arbiter control register is used for the bridge internal arbiter. The arbitration scheme used is a two-tier rotational
arbitration. The PCI2050 bridge is the only secondary bus initiator that defaults to the higher priority arbitration tier.
Bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Name Arbiter control
Type R R R R R R R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W
Default 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0
Register: Arbiter control
Type: Read-only, Read/Write
Offset: 42h
Default: 0200h
Table 5–3. Arbiter Control Register Description
BIT TYPE FUNCTION
15–10 R Reserved. Bits 15–10 return 0s when read.
9 R/W
Bridge tier select. This bit determines in which tier the PCI2250 bridge is placed in the two-tier arbitration scheme.
0 = Low priority tier
1 = High priority tier (default)
8 R/W
GNT8 tier select. This bit determines in which tier the S_GNT8 is placed in the arbitration scheme. This bit is encoded as:
0 = Low priority tier (default)
1 = High priority tier
7 R/W
GNT7 tier select. This bit determines in which tier the S_GNT7 is placed in the arbitration scheme. This bit is encoded as:
0 = Low priority tier (default)
1 = High priority tier
6 R/W
GNT6 tier select. This bit determines in which tier the S_GNT6 is placed in the arbitration scheme. This bit is encoded as:
0 = Low priority tier (default)
1 = High priority tier
5 R/W
GNT5 tier select. This bit determines in which tier the S_GNT5 is placed in the arbitration scheme. This bit is encoded as:
0 = Low priority tier (default)
1 = High priority tier
4 R/W
GNT4 tier select. This bit determines in which tier the S_GNT4 is placed in the arbitration scheme. This bit is encoded as:
0 = Low priority tier (default)
1 = High priority tier
3 R/W
GNT3 tier select. This bit determines in which tier the S_GNT3 is placed in the arbitration scheme. This bit is encoded as:
0 = Low priority tier (default)
1 = High priority tier
2 R/W
GNT2 tier select. This bit determines in which tier the S_GNT2 is placed in the arbitration scheme. This bit is encoded as:
0 = Low priority tier (default)
1 = High priority tier
1 R/W
GNT1 tier select. This bit determines in which tier the S_GNT1 is placed in the arbitration scheme. This bit is encoded as:
0 = Low priority tier (default)
1 = High priority tier
0 R/W
GNT0 tier select. This bit determines in which tier the S_GNT0 is placed in the arbitration scheme. This bit is encoded as:
0 = Low priority tier (default)
1 = High priority tier