BCM1250/BCM1125/BCM1125H
User Manual
10/21/02
B r o a d c o m C o r p o r a t i o n
Page
230
Section 8: PCI Bus and HyperTransport Fabric
Document
1250_1125-UM100CB-R
12.2 Low Level Link Initialization and Table 54 Values of CTL and CAD During Link Initialization
Sequence
The transmit side will generate 512 cycles with CTL and CAD as zero before asserting CAD
and the receive side will accept 512+M cycles. This matches both the older versions of the spec
which need 'a minimum of 512 cycles' and can have an arbitrary number of additional bit times,
and the newer version '512+4N' where the minimum is still 512 cycles (N=0) but any additional
duration of CTL and CAD at zero must be for a multiple of four bit times.
12.3 I/O Fabric Initialization
Since the MIPS architecture does not support non-posted writes the TgtDone counter has been
added to allow detection of the completion of configuration writes.
In a Double-hosted chain software is responsible for determing which is the master and slave
ends of the fabric and performing appropriate configuration.
12.3.1 Finding the Firmware ROM
The part cannot boot from a ROM over the HyperTransport link.
12.5 Link Frequency Initialization
The interface will normally perform the link frequency change on a link reset, and revert to
200MHz on a cold reset. However, to support other devices that use the HyperTransport
specification from before revision 1.0 this behaviour can be prevented by setting the
sriLdtPLLCompat bit in the SRI Command Register (
).
A. Address Remapping
The interface supports the host address map as outlined throughout this chapter, so does not
need the address remapping scheme.
B. Ordering Rules
The HyperTransport interface uses the PCI ordering rules.
C. Mapping of Other Protocol Ordering Rules
The interface maps from the ZBbus as described in C.1. Non-posted writes are not part of the
MIPS architecture and so will never be generated for memory-mapped I/O.
D. Considerations for Isochronous Traffic
The interface does not use the new isochronous scheme. The isochronous bit from DMA read
or write requests is copied into the L2CA flag for the ZBbus transaction. Isochronous requests
will therefore cause L2 allocation on a miss.
The part always generates requests with the isochronous bit clear.
E.1, E.2 ISA/LPC Support
There is no special ISA/LPC support. All warnings and restrictions in these sections must be
followed.
Note that PCI devices that only support Revison 2.0 or earlier of the PCI Specification may
have similar problems to ISA devices since they do not support the full ordering and transaction
acceptance rules.