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
260
Section 8: PCI Bus and HyperTransport Fabric
Document
1250_1125-UM100CB-R
The registers that make up the HyperTransport Bridge header are reset by both system resets and are
unaffected by link reset with the following exceptions:
1
The HyperTransport SRI Command Register is reset on system cold reset and persistent across system warm
reset.
2
The following bits in the HyperTransport Bridge Secondary Status Register are set to zero on a system cold
reset and are persistent through a system warm reset: SigdTgtAbort, RcvdTgtAbort, RcvdMstrAbort, DetSerr.
3
The following bits in the HyperTransport Link Control Register are reset by link reset: InitDone, EOC, XmitOff.
4
The LinkFail bit and CrcErr bits in the HyperTransport Link Control Register are reset to zero on a system cold
reset and are persistent through a system warm reset.
5
The HyperTransport Link Frequency Register is cleared by system cold reset and is persistent across system
warm reset. Beyond that, it's behavior is determined by the sriLdtPLLCompat bit in the HyperTransport SRI
Command Register. If the sriLdtPLLCompat bit is set, the Link Frequency implementation becomes backwards
compatible with HyperTransport Specification revision 0.17, which does not allow for dynamic frequency
negotiation. In this mode, the HyperTransport link must come up at a static frequency and therefore writes to
the LinkFrequency Register take effect immediately. It is strongly suggested that this be done prior to setting
the SipReady bit in the HyperTransport SRI Command Register and at no other time. If the sriLdtPLLCompat
bit is clear, a write to the Link Frequency Register will take effect only on the next link warm reset.