MVME5100 Single Board Computer Programmer's Reference Guide

Functional Description
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. Table 2-10
describes all available settings for the “HEIR” field in fixed mode.
Table 2-10. Fixed Mode Priority Level Setting
HEIR
Priority Levels
Setting Highest Lowest
000 PARB6 PARB5 PARB4 PARB3 PARB2 PARB1 PARB0 HAWK
001 HAWK PARB6 PARB5 PARB4 PARB3 PARB2 PARB1 PARB0
010 PARB0 HAWK PARB6 PARB5 PARB4 PARB3 PARB2 PARB1
011 PARB1 PARB0 HAWK PARB6 PARB5 PARB4 PARB3 PARB2
100 PARB2 PARB1 PARB0 HAWK PARB6 PARB5 PARB4 PARB3
101 PARB3 PARB2 PARB1 PARB0 HAWK PARB6 PARB5 PARB4
110 PARB4 PARB3 PARB2 PARB1 PARB0 HAWK PARB6 PARB5
111 PARB5 PARB4 PARB3 PARB2 PARB1 PARB0 HAWK PARB6
Notes 1. “000” is the default setting in fixed mode.
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.
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