2. Interface Operation
44
Tsi308 User Manual
80D4000_MA001_02
Tundra Semiconductor Corporation
www.tundra.com
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Tsi308 generates one or more split completion transactions until the byte count of the
original request is satisfied.
2.4.9
Continuous Prefetching (PCI mode only)
If continuous prefetching is enabled in the Read Control CSR, the Tsi308 issues further
ascending read requests to fill buffers as they drain (up to a 4-KB page boundary) in an effort to
make sure required data is always available. Otherwise, the transaction is disconnected as soon
as all data from the initial reads is returned to the PCI bus.
2.4.10
Transaction Disconnects
Read transactions may be disconnected by the bridge when required data is not available in
time. The Delayed Request buffer remains in use until all outstanding HyperTransport prefetch
requests receive their responses; then it is retired and any leftover data is discarded (PCI mode
only). Each delayed request buffer also has an associated discard timer loaded with one of the
two values determined by the Secondary Discard Timer bit (9) of the Bridge Control CSR (3Eh)
when the data is received from HyperTransport. If this timer expires before the data is called for
by the PCI master, the data is discarded and the buffer is retired.
2.4.11
Outbound Data Buffer
The Tsi308 contains a central data buffer (four 512-byte entries) for the accumulation of read
response data to return to the PCI-X bus. These four buffers correspond to four read requests in
Delayed Request Buffers. Data returning from HyperTransport is loaded into the buffer based
on the comparison between request information stored in the corresponding delayed request
number and information contained in response header, and drained out to the PCI-X bus when
the delayed request reconnects (PCI) or when the Tsi308’s split completer connects.
2.4.12
Interrupt Generation
The Tsi308 interrupt controller supports 10 interrupts per PCI-X port. Each of these interrupts
are enabled and configured independently through its Interrupt Definition Register CSR.
However Tsi308 while operating in Tsi301 compatible mode, these interrupts are partitioned
into different groups, each group consists of four interrupts or less and interrupts are configured
in groups. The interrupt configuration options include: edge versus level sensitivity, polarity,
and vector ID.
An incoming interrupt is first synchronized to the core clock domain and masked with its CSR
enable bit to set the interrupt’s bid in the Interrupt Request Register (IRR). A round-robin arbiter
will then examine each IRR bit and forward requests to the primary bus logic, setting its In
Service Register (ISR) bit. New interrupts from that pin will not be accepted as long as the ISR
register is set.
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For edge sensitive interrupts, the ISR bit is cleared as soon as the primary interface logic
accepts the inbound interrupt request
Содержание TSI308
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