000-0046140-111
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SLG46140
21.0 Oscillators
The SLG46140 has two internal RC oscillators (25 kHz or 2 MHz, user selectable), as well as one Low-Frequency oscillator
(1.9 kHz) and one Ring oscillator (25 MHz).
There are two divider stages for the RC and Ring oscillators, and one divider stage for the Low-Frequency oscillator, that allow
the user flexibility for introducing clock signals to connection matrix, as well as various other Macrocells. The predivider (first
stage) for RC Oscillator allows the selection of /1, /2, /4 or /8, for LF Osc - /1, /2, /4 or /16 and for Ring Osc - /1, /4, /8 or /16 to
divide down frequency from the fundamental. The second stage divider of RC oscillators has an input of frequency from the
predivider, and outputs one of eight different frequencies on Connection Matrix Input line <35>. The output of LF Osc Predivider
goes directly on Connection Matrix Input line <50>. Please see
below, for more details on the SLG46140 clock scheme.
The Matrix Power Down function allows to switch on/off the oscillators using an external pin (reg<567> for 25 kHz / 2 MHz OSC,
reg<562> for LF OSC and reg<575> for Ring Osc):
•
Enable <1>
. If PWR DOWN input of oscillator is LOW, the oscillator will be turned on. If PWR DOWN input
of oscillator is HIGH the oscillator will be turned off.
•
Disable <0>
. Turns off the Matrix Power Down function.
The PWR CONTROL signal has the highest priority.
The user can select two OSC POWER MODEs (reg<564> for 25 kHz / 2 MHz RC OSC, reg<563> for LF OSC and reg<574> for
Ring Osc):
•
If FORCE POWER ON <1>
is selected, the OSC will run when the SLG46140 is powered on.
•
If AUTO POWER ON <0>
is selected, the OSC will run only when any macrocell that uses OSC is powered on.
OSC can be turned on by:
•
Register control (force power on);
•
Delay mode, when delay requires OSC;
•
ADC;
•
PWM/DCMP.