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STP2002QFP
Fast Ethernet, Parallel Port, SCSI (FEPS) - STP2002QFP
Sun Microsystems,
machine. After this the arbiter is available to arbitrate and grant the next re-
quest on the CEI provided that there is a DMA write or read buffer still avail-
able. The master port state machine wakes up and request the SBus whenever
there is a request in the queue. When SBus is granted, the master port state
machine assertedBG to the corresponding CE and pass the read data over to
the CEI bus.
2.3.2 Slave Operation
When bothAS and SEL input signals are asserted, the slave port begin to re-
spond to the slave access from the SBus. Based on the physical address, one
of the channel engines is selected to respond to the slave access. Slave writes
goes directly through to the CEI bus without arbitration because it share the
CEI data-in data bus with DVMA read which is mutually exclusive to slave
operation. Slave reads share the CEI data-out bus with all other CEI opera-
tions and have to go through arbiter to compete with channel engines.
Because a SBus DVMA read operation may encounter a retry, there is con-
dition that a CE is being granted with DVMA read and a slave access still
comes in. The CE has to make sure that it can still respond to this slave access
under this condition.