MPC555CME Freescale Semiconductor, MPC555CME Datasheet - Page 329

• Manufacturer Part Number: MPC555CME
• Description: KIT EVALUATION FOR MPC555
• Manufacturer: Freescale Semiconductor
• Type: Microcontrollerr

Specifications of MPC555CME

• Contents: Module Board, Installation Guide, Power Supply, Cable, Software and more
• Processor To Be Evaluated: MPC555
• Data Bus Width: 32 bit
• Interface Type: RS-232
• For Use With/related Products: MPC555
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

9.5.6.4 Internal Bus Arbiter
MPC555
USER’S MANUAL
CLKOUT
BR0
BG0
BR1
BG1
BB
ADDR & Attr.
TS
TA
The MPC555 / MPC556 can be configured at system reset to use the internal bus ar-
biter. In this case, the MPC555 / MPC556 will be parked on the bus. The parking fea-
ture allows the MPC555 / MPC556 to skip the bus request phase, and if BB is negated,
assert BB and initiate the transaction without waiting for BG from the arbiter.
The priority of the external device relative to the internal MPC555 / MPC556 bus mas-
ters is programmed in the SIU module configuration register. If the external device re-
quests the bus and the MPC555 / MPC556 does not require it, or if the external device
has higher priority than the current internal bus master, the MPC555 / MPC556 grants
the bus to the external device.
Table 9-4
/
MPC556
describes the priority mechanism used by the internal arbiter.
Figure 9-25 Bus Arbitration Timing Diagram
“Turns On” and
Drives Signals
Master 0
EXTERNAL BUS INTERFACE
Rev. 15 October 2000
(Three-state Controls)
and “Turns Off”
Negates BB
Master 0
“Turns On” and
Drives Signals
Master 1
MOTOROLA
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