Power Management
15-41
Clock Generation and System Reset Management
9) Read hi_freq counter value:
Read counter_hi_freq_msb and counter_hi_freq_lsb registers.
10) Compare values of the counter and proceed with calibration of the 32-kHz
counter.
At the end of the gauging operation, an END_GAUGING interrupt informs the
MCU that gauging is stopped and values of the counters are ready to be read.
This interrupt is low-level sensitive. It is cleared on the reading of these
registers.
Two other low-level-sensitive interrupts indicate whether an overflow occurred
on one of the two counters during the gauging operation. One interrupt is dedi-
cated for the 32-kHz counter, the second one for the high-frequency counter.
They are also cleared on the read of the interrupt status register.
15.3.6.3
Control of 32-kHz Oscillator
The 32-kHz oscillator start-up time is configurable via the bits
MOD_32KOSC_SW_R bits of the module configuration control 0 register
(MOD_CONF_CTRL_0) in OMAP5910 configuration.
The 32kHz clock source can come from either the on-chip 32-kHz oscillator
or from an external 32-kHz clock oscillator providing a clock onto the
CLK32K_IN input pin. Clock source selection depends upon the state of the
CLK32K_CTRL input pin. If this pin is driven (or tied) high, the on-chip 32-kHz
oscillator is enabled as the clock source. If the pin is driven (or tied) low, then
the clock must be provided externally on the CLK32K_IN pin.
MOD_32KOSC_SW_R is a 4-bit field that sets the performance control
switches of the oscillator 32-kHz (SW1, SW2, SW3, SW4). Table 15–4 lists the
recommended control switch settings:
Table 15–4. Recommended Control Switch Settings
Oscillator Performance
SW4
SW3
SW2
SW1
Least current
1
0
0
0
Fast startup
1
0
1
1