82375EB Datasheet, PDF (91/131 Pages) Intel Corporation – PCI-EISA BRIDGE (PCEB)

82375EB SB
As a master the PCEB does not know if it is accessing the same target and thus does not generate fast
back-to-back accesses As a slave the PCEB is capable of decoding fast back-to-back cycles
Figure 23 Arbitration for Back-to-Back Access
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5 4 3 RETRY THRASHING RESOLVE
When a PCI initiator’s access is retried the initiator releases the PCI Bus for a minimum of two PCI clocks and
then normally requests the PCI Bus again To avoid thrashing of the bus with retry after retry the PCI arbiter’s
state tracer provides REQ masking Tracking retried masters requires latching GNT during FRAME so
that the correct retried master can be masked The state tracer masks a REQ after that particular agent is
retried on the PCI Bus The state tracer differentiates between two retry events The two events include PCEB
target retries and all other retries
For initiators that were retried by the PCEB as a target the masked REQ is flagged to be cleared upon
RESUME active All other retries trigger the Master Retry Timer (described in Section 5 4 4 2 Master Retry
Timer) When this timer expires the mask is cleared
5 4 3 1 Resume Function
The PCEB forces a retry to a PCI master (resulting in masking the REQ of that master) for the following
1 Buffer management activities (See Section 6 0 Data Buffering)
2 The EISA Bus is occupied by an EISA ISA master or DMA
4 The PCEB is locked as a resource and PLOCK is asserted during the address phase
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