MPC563XM Reference Manual, Rev. 1
Freescale Semiconductor
363
Preliminary—Subject to Change Without Notice
shows example timing for the case of two masters connected to a central arbiter. In this case,
the BR0 & BR1 signals shown are inputs to the arbiter from the BR pin of each master. The BG0 & BG1
signals are outputs from the arbiter that connect to the BG pin of each master.
Figure 13-34. Central Arbitration Timing Diagram
13.5.2.8.2
Internal Bus Arbiter
When an MCU is configured to use the internal bus arbiter, that MCU is parked on the bus. The parking
feature allows the MCU to skip the bus request phase, and if BB is negated, assert BB, and initiate the
transaction without waiting for bus grant from the arbiter. The priority between internal and external
masters over the external bus is determined by the EARP field of the EBI_MCR. See
EARP field description.
CLKOUT
BR0
BG1
ADDR + ATTR
BG0
BR1
BB
TS
TA
Both masters configured for external arbitration
M0 receives bus grant and bus busy negated for 2nd cycle
M1 receives bus grant and bus
busy negated for 2nd cycle
Both
Masters
off
CSx
Master 0
and “turns on”
Master 0
negates BB
and “turns off”
(drives controls)
(three-states
controls)
asserts BB
Master 1
and “turns on”
(drives controls)
asserts BB