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21555 Non-Transparent PCI-to-PCI Bridge User Manual 183
List of Registers
16.11 Arbiter Control
This chapter describes the arbitration control registers. See Chapter 10 for theory of operation information.
16.12 Error Registers
This section describes the primary and secondary SERR# disable registers. See Chapter 12 for theory of operation
information.
Table 115. Arbiter Control Register
This register may be preloaded by serial ROM or programmed by local processor before host configuration.
• Primary byte offset: D3:D2h
• Secondary byte offset: D3:D2h
Bit Name R/W Description
9:0 Arbiter Control R/W
Each bit controls whether a secondary bus master is assigned to the high
priority arbiter ring or the low priority arbiter ring. Bits [8:0] correspond to
request inputs s_req_l[8:0], respectively. Bit [9] corresponds to the internal
21555 secondary bus request.
• When 0, indicates that the master belongs to the low priority group.
• When 1, indicates that the master belongs to the high priority group.
• Reset value is 10 0000 0000b.
10
Bus Parking
Control
R/W
Controls whether the 21555 parks on itself or on the last master to use the
bus.
• When 0, during bus idle, the 21555 parks the bus on the last master to
use the bus.
• When 1, during bus idle, the 21555 parks the bus on itself. The bus
grant is removed from the last master and internally asserted to the
21555.
• Reset value is 0b.
15:11 Reserved R Reserved. Returns 0 when read.