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MPC563XM Reference Manual, Rev. 1
Freescale Semiconductor
367
Preliminary—Subject to Change Without Notice
shows the internal finite state machine that implements the arbiter protocol.
5
This represents an internal EBI signal that indicates whether the Internal MCU (0) or External master (1) currently has
higher priority.
6
This represents an internal EBI signal that indicates whether an EBI-mastered transaction on the bus is in progress this
cycle or is going to start the next cycle (and thus has already been committed internally).
7
This represents an internal EBI signal that indicates whether the bus was granted to an external master (BG=0, previous
BB=1) during the previous 3 cycles.
8
RGB is always low in this state, thus it is ignored in the transition logic.
9
RGB is always low in this state, thus it is ignored in the transition logic.
10
The ETP signal is never asserted in states where it is shown as an "X" for all transitions.
11
RGB is always high in this state, thus it is ignored in the transition logic.
12
IRP is ignored (treated as 1) in the MCU_WAIT state because the EBI does not optimally support an internal master
cancelling its bus request. If IRP is negated in this state, the EBI still grants the internal master the bus as if IRP was still
asserted, and a few cycles may be wasted before the external master may be able to grab the bus again (depending on
BR, BB, etc., according to normal transition logic).
13
The default BB output is 0 for this state. However, anytime the EBI transitions from a state where BB=0 to a state where
BB=hiZ, there is one external cycle (in this state) where the EBI drives BB=1 to actively negate the pin before letting go
to hiZ. In the case where a second granted internal request (IRP=1, ETP=1) is ready to start just before the transition to
the hiZ state would otherwise have occurred (during the BB=1active negate cycle), then BB is driven back to 0 to start the
next access without ever leaving this state or going to hiZ.
14
BR is ignored (treated as 0) in the EXT_WAIT state because the EBI does not optimally support an external master
cancelling its bus request. If BR is negated in this state, the EBI still grants the external master the bus as if BR was still
asserted, and a few cycles may be wasted while the external master "window-of-opportunity" is satisfied before the
internal master may be able to grab the bus again (depending on BR, BB, etc., according to normal transition logic).