Table 2-10. Fixed Mode Priority Level Setting - Motorola MVME5100 Programmer's Reference Manual

The Hawk's PCI arbiter has various programming options. It supports 3
different priority schemes: fixed, round robin, and mixed mode. It also
allows various levels of reprioritization programming options within fixed
and mixed modes. Parking can be programmed to any of the requestors, the
last requestor or none. A special bit is added to hold grant asserted for an
agent that initiates a lock cycle. Once a lock cycle is detected, the grant is
held asserted until the PCI LOCK_ pin is released. This feature works only
when the "POL" bit is enabled.
The priority scheme can be programmed by writing the "PRI" field in the
PCI Arbiter control register. The default setting for priority scheme is fixed
mode. The Fixed mode holds each requestor at a fixed level in its
hierarchy. The levels of priority for each requestor are programmable by
writing the "HEIR" field in the PCI Arbiter control register.
describes all available settings for the "HEIR" field in fixed mode.

Table 2-10. Fixed Mode Priority Level Setting

HEIR
Setting
Highest
000 PARB6 PARB5
001 HAWK PARB6
010 PARB0 HAWK
011 PARB1 PARB0
100 PARB2 PARB1
101 PARB3 PARB2
110 PARB4 PARB3
111 PARB5 PARB4
Notes 1. "000" is the default setting in fixed mode.
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Priority Levels
PARB4 PARB3
PARB5 PARB4
PARB6 PARB5
HAWK PARB6
PARB0 HAWK
PARB1 PARB0
PARB2 PARB1
PARB3 PARB2
2. The HEIR setting only covers a small subset of all possible
combinations. It is the responsibility of the system designer
to connect the request/grant pair in a manner most beneficial
to their design goals.
Functional Description
PARB2 PARB1 PARB0
PARB3 PARB2 PARB1
PARB4 PARB3 PARB2
PARB5 PARB4 PARB3
PARB6 PARB5 PARB4
HAWK PARB6 PARB5
PARB0 HAWK PARB6
PARB1 PARB0 HAWK
2
Table 2-10
Lowest
HAWK
PARB0
PARB1
PARB2
PARB3
PARB4
PARB5
PARB6
2-35