ÉlanSC310 Microcontroller Evaluation Board User’s Manual
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The state of the PMC pins can be set for each PMU mode. While the particular
state the PMC pin is in does not significantly affect the ÉlanSC310
microcontroller’s power consumption, this matrix allows the user to see what
control the user has for external control of the PMC pins for each PMU mode. Note
that the PMC pin setting for the Low and High Speed PLL modes mirror each
other. Changing the value in one column causes the value in the other column to
change also.
High Speed PLL Mode Column
• The CPU speed can be set to 33 Mhz, 25 Mhz, 20 Mhz, or 9.2 Mhz.
• Both the High Speed and Low Speed PLLs for this mode are enabled.
• The state of the PMC pins for this mode mirror the settings in Low Speed PLL
mode. Changing the state in this mode also changes the state for Low Speed
PLL mode.
• Auto Low Speed mode, when enabled, switches the CPU clock speed to operate
at 9.2 Mhz for the duration of time listed in ALS Duration matrix item (0.25,
0.50, 1.0, 2.0 seconds). This switch is triggered at a rate determined by the ALS
Trigger matrix item, which can be set to 4, 8, 16, or 32 seconds. The ALS trigger
period and ALS Duration time are stored in write-only registers. Therefore it is
not possible to read the current ÉlanSC310 programed value when this utility
is started. The default values of 4 seconds for the ALS Trigger and 0.25 seconds
for the ALS Duration are programmed at start-up time.
• The CPU Idle Speed can be set to "HIGH" or "LOW." "HIGH" means that during
idle cycles the CPU runs at the current High Speed CPU speed (33, 25, 20, or
9.2 Mhz); "LOW" means 9.2 Mhz. The CPU Idle Speed can only be set "LOW"
if the High Speed CPU is set to 20 Mhz or 9.2 Mhz. If the High Speed CPU
speed is set to 33 Mhz or 25 Mhz and the CPU Idle Speed is then set to "LOW",
the CPU speed changes to 20 Mhz. Similarly, if the CPU Idle Speed is set to
"LOW" and the High Speed CPU speed is changed to 33 Mhz or 25 Mhz, the
CPU Idle speed is changed to "HIGH."
evalbd.book : ch3 Page 6 Thursday, August 8, 1996 2:34 PM