Motorola MPC8260 PowerQUICC II, User Manual

Page: 454 / 1006

13-24 MPC8260 PowerQUICC II UserÕs Manual MOTOROLA
Part IV. Communications Processor Module
13.6.10 Using the RISC Timers to Track CP Loading
The RISC timers can be used to track CP loading. The following sequence provides a way
to use the 16 RISC timers to determine if the CP ever exceeds the 96% utilization level
during any tick interval. Removing the timers adds a 4% margin to the CP utilization level,
but the aggressive user can use this technique to push CP performance to its limit. The user
should use the standard initialization sequence and incorporate the following differences:
1. Program the tick of the RISC timers to be every 1,024 x 16 = 16,384 system clocks.
2. Disable RISC timer interrupts, if preferred.
3. Using the
SET TIMER
command, initialize all 16 RISC timers to have a timer period
of 0xFFFF, which equates to 65,536.
4. Program one of the four general-purpose timers to increment once every tick. The
general-purpose timer should be free-running and should have a timeout of 65,536.
5. After a few hours of operation, compare the general-purpose timer to the current
count of RISC timer 15. If it is more than two ticks different from the
general-purpose timer, the CP has, during some tick interval, exceeded the 96%
utilization level.
NOTE:
General-purpose timers are up counters, but RISC timers are
down counters. The user should take this under consideration
when comparing timer counts.