Datasheet

Bus Operation
6-66 MCF5206e USER’S MANUAL MOTOROLA
NOTES:
1)“N” means negated; “A” means asserted; “EM” means external master.
2)End of Cycle: Whatever terminates a bus transaction whether it is normal or bus error. Note that bus cycles that
result from a burst inhibited transfer are considered part of that original transfer.
3)IBR refers to an internal bus request.The output signals BR is a registered version of IBR when BG is negated and
BD
is negated. There is an internal bus request when the Coldfire core requires the external bus for an operand
transfer
.
The MCF5206e can be in any one of four arbitration states during bus operation: reset,
external master own, implicit ownership, and explicit ownership.
The reset state is entered whenever RSTI
or software watchdog reset is asserted in any
bus arbitration state. When RSTI and the software watchdog reset are negated, the
MCF5206e proceeds to the implicit ownership state or external master ownership state,
depending on bus grant (BG).
The external master ownership state denotes the MCF5206e does not have ownership
(bus grant (BG) negated) of the bus and the MCF5206e does not drive the bus. The
Table 6-12. MCF5206e Three-Wire Bus Arbitration Protocol Transition Conditions
PRESENT
STATE
CONDITION
LABEL
RSTI
SOFTWARE
WATCHDOG
RESET
BG
BUS LOCK
BIT
INTERNAL
BUS REQUEST
(IBR
)
TRANSFER IN
PROGRESS
END OF
CYCLE
NEXT STATE
RESET
A1 A - - - - - - Reset
A2 N A - - - - - Reset
A3 N N N - - - - EM Own
A4 N N A - - - - Implicit Own
IMPLICIT OWN
B1 N N N - - - - EM Own
B2 N N A A - - - Explicit Own
B3 N N A N N - - Implicit Own
B4 N N A - A - - Explicit Own
EXPLICIT OWN
C1 N N A - - - - Explicit Own
C2 N N N Y - - - Explicit Own
C3 N N N N - N - EM Own
C4 N N N - - Y N Explicit Own
C5 N N N N - Y Y EM Own
EM OWN
D1 N N N - - - - EM Own
D2 N N A A - - - Explicit Own
D3 N N A N N - - Implicit Own
D4 N N A N A - - Explicit Own
Table 6-13. MCF5206e Three-Wire Arbitration Protocol State Diagram
STATE OWN BUS STATUS BD
Reset No Not Driven Negated
Implicit Own Yes Not Driven Negated
Explicit Own Yes Driven Asserted
EM Own No Not Driven Negated
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