mcf51jf128 Freescale Semiconductor, Inc, mcf51jf128 Datasheet - Page 329

• Manufacturer Part Number: mcf51jf128
• Description: Mcf51jf128 Reference Manual
• Manufacturer: Freescale Semiconductor, Inc

Chapter 14 Crossbar Switch
This functionality allows the user to automatically elevate a master port's priority level
throughout the crossbar to quickly perform temporary tasks such as servicing interrupts.
However, when using this functionality take care to not to occupy 100% of a slave's
bandwidth with one master, and essentially locking out the rest of the masters. This
should only be used for important temporary tasks, such as interrupt handling.
14.3.2.4.1 Priority Elevation in Round-Robin Mode
If a slave port is programmed for round-robin mode and a master is configured for
priority elevation, that master can force the slave port into fixed priority mode. The slave
port remains in fixed priority mode while that master's (or any other master's) configured
for priority elevation and it attempts access to that particular slave port.
After the masters are no longer configured for priority elevation, or the masters no longer
attempt accesses to that particular slave port, the slave port reverts to round-robin priority
mode. Then, the pointer is set on the last master to access the slave port.
14.4 Initialization/Application Information
No initialization is required by or for the crossbar switch.
MCF51JF128 Reference Manual, Rev. 2, 03/2011
Preliminary
Freescale Semiconductor, Inc.
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