AN2667 Freescale Semiconductor / Motorola, AN2667 Datasheet - Page 14

• Manufacturer Part Number: AN2667
• Description: Multi-Controller Hardware Development for the MPC5xx Family
• Manufacturer: Freescale Semiconductor / Motorola

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The following analysis considers the MPC561/3 as per the EVB. The points
highlighted also apply to the MPC555 and MPC565.
2 x MPC561:
There is a performance hit when the master accesses the slave. This is because the master
needs the EBI to do this. This means it cannot fetch instructions from external memory at the
same time as accessing the slave. Note that if both devices had to share the same external
memory for instructions the overall system performance would be less than that of a single device
due to the bus arbitration required.
As the MPC561 has no internal flash memory it cannot use the flash RCW. As the master device
will be executing instructions from external memory it makes sense for the master to take the
default RCWand allow the slave to take its from the data bus.
1x MPC563 & 1x MPC561:
There is still a performance hit if the master accesses the external slave. The data access to the
slave freezes the internal UBUS,which prevents instruction fetches from internal flash.
The master can now take its RCW from the internal flash memory. The slave code size is limited
to the size of the internal CALRAM. This is a cost effective solution.
2 x MPC563:
As above there is the same performance hit.
There are more options for RCW as each device can have its RCW located in internal flash
memory. This is a simpler solution as both RCWs can be stored internally and the code for each
device can be stored internally.
If the slave code is bigger than the internal CALRAM then 512K flash memory is available. This
solution will be slightly more expensive than the others.
MOTOROLA
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The Dual MPC561-4 Evaluation Board has the following specification:
– MC33394 (PowerOak) Regulator
– 20MHz Xtal
– 2 x MPC561/2/3/4 sockets
– 2 x Mode Config Switches(MODCK settings) + 32 RCW Switches
– 2 x NEXUS + 2 x BDM
– 3 x Mictor Connectors
– 6 x CAN(5 stand alone and 1 integrated with the MC33394)
–
Performance Impact On a Dual Controller System
EVB Overview
2 x RS232 9 way D type connectors
Multi-Controller Hardware Development for the MPC5xx Family
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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