MPC555CME Freescale Semiconductor, MPC555CME Datasheet - Page 191

• 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

4.4.1 Normal Operation
4.4.2 Slave Operation.
4.4.3 Reset Operation
4.4.4 Debug Mode Operation
4.4.5 Standby Mode Operation
4.4.6 Burst Operation
MPC555
USER’S MANUAL
During normal operation, the burst buffer module transfers fetch accesses from the
CPU to the U-bus. When a new access is issued by the CPU, it is transferred in parallel
to both the IMPU and the BBC. The IMPU compares the address of the access to its
region programming. The BBC determines whether the access can be immediately
transferred to the U-bus. If not, it requests the U-bus for the next clock.
Each new BBC U-bus access is accompanying by the burst request attribute. If burst-
able access is enabled, the BBC performs a burst access; otherwise, it performs a sin-
gle access.
If the IMPU detects an access violation, it does the following:
If the required address contains show cycle or program trace attributes, the BBC de-
livers the access to the U-bus even if the request is cancelled (due to the exception it
caused).
The BBC forwards show cycle, program trace and debug port access attributes ac-
companying the CPU access along with the U-bus access.
The burst buffer module is operating as a U-bus slave module when the instruction
memory protection unit (IMPU) registers are accessed by the user in order to be pro-
grammed. This programming is done using the mtspr /mfspr instructions.
On reset the BBC goes to an idle state, and all pending U-bus accesses are ignored.
The IMPU goes to a disabled state in which all memory space is accessible to both
user and supervisor.
When the CPU is in debug mode, fetch accesses are attached with a special attribute.
If this attribute is asserted, the BBC must initiate not-burstable accesses to the debug
port.
In this low-power mode the CPU stops issuing further accesses. The BBC clocks are
turned off, and the BBC enters a power-save state. When the low-power mode is ex-
ited, clocks are activated and a new access from the CPU will activate the BBC.
The BBC can run burst accesses on the U-bus. Such burst cycles, if forwarded to ex-
ternal memory, are then exported to the EBI as burst cycles (if bursts are enabled by
the USIU).
• Cancels the request that was forwarded to the BBC
• Informs the RCPU core that the requested address generated an exception
/
MPC556
Rev. 15 October 2000
BURST BUFFER
MOTOROLA
4-15