2. Interface Operation
41
Tsi308 User Manual
80D4000_MA001_02
Tundra Semiconductor Corporation
www.tundra.com
Memory mapped addresses are compared to the range defined by the Memory Range Base Addr
and Memory Range Limit Addr CSRs; and the range defined by the Prefetchable Memory
Range Base Upper and Prefetchable Memory Range Base Addr, and Prefetchable Memory
Range Limit Upper and Prefetchable Memory Range Limit Addr CSRs. Addresses that don’t
fall into any of these ranges are accepted for forwarding to HyperTransport as long as the
MasterEn bit in Command CSR is set and bits [39:32] <= FCh.
•
I/O Cycles. The Tsi308 implements a 64-bit space for I/O accesses. While operating in
Tsi301 compatible mode, address bits above bit 24 are ignored and result in 25-bit space
aliasing through PCI’s 32-bit I/O space.
I/O addresses are compared to the range defined by I/O Range Base Upper and I/O Base, and
I/O Range Limit Upper and I/O Limit CSRs. Accesses that miss the range are accepted for
forwarding to HyperTransport, as long as MasterEn bit in the Command CSR is set.
•
Configuration and Special Cycles. The Tsi308 never acts as a target for configuration or
special cycles on PCI-X bus.
2.4.2
PCI-X Posted Write Queue
The Tsi308 responds as a PCI-X write target to PCI-X Memory Write, Memory Write
Invalidate, and I/O Write commands. All of these writes are posted to the HyperTransport chain
except I/O writes which is non-posted. The Tsi308 never responds to Configuration Writes. A
total of 1024 bytes of buffering for posted data is provided per PCI-X bus.
Memory Write and Memory Write Invalidate commands stream data into the chip,
disconnecting either on 4-KB boundaries or when all of the internal buffer space is filled. The
Tsi308 generates the largest HyperTransport write operations possible, issuing them
continuously as the data for each write is received from PCI-X.
As the bandwidth of HyperTransport exceeds the bandwidth of PCI-X, it is expected that the
internal buffers will not fill and memory writes will proceed continuously at the full bandwidth
of PCI-X bus.
2.4.3
PCI-X Delayed/Split Request Buffers
The Tsi308 acts as a PCI-X target for PCI-X Memory Read, Memory Read Line (PCI), Memory
Read Multiple (PCI), Memory Read Block (PCI-X), I/O Write and I/O Read commands. The
Tsi308 never responds to configuration read or interrupt acknowledge accesses. All supported
read transactions are implemented as delayed requests (PCI) or split requests (PCI-X).
Incoming requests are assigned to a delayed request buffer. There are four delayed request
buffers, enabled under CSR control, allowing up to four PCI-X read requests to be in progress at
one time. If no delayed request buffers are free, incoming requests are retried until one is
available. Once the request is assigned to a buffer, the interface continues to retry it on the PCI
bus while read requests are issued to the HyperTransport interface.
Summary of Contents for TSI308
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