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15.0
Real Time Clock (RTC) Interface
15.1
RTC Interface
The EP80579 contains a Real Time Clock (RTC) with 256 bytes of battery-backed SRAM.
The internal RTC module provides two key functions:
• keeping the date and time
• storing system data in its RAM when the system is powered down
The RTC module uses a crystal circuit to generate a low-swing 32 KHz input sine wave.
This input is amplified and driven back to the crystal circuit via the RTCX2 signal.
Internal to the EP80579, the RTCX1 signal is amplified to drive internal logic as well as
generate a free-running, full-swing clock output for system use. This output signal of
the EP80579 is called SUSCLK, as illustrated in
Figure 129. RTCX1 and SUSCLK Relationship in EP80579
Low-Swing 32.768 KHz
Sine W ave Source
Full-Swing 32.768 KHz
Output Signal
15.1.1
RTC Crystal
The RTC module requires an external oscillating source of 32.768 KHz connected to the
RTCX1 and RTCX2 signals.
oscillator of the RTC:
®
Intel
EP80579 Integrated Processor Product Line
Platform Design Guide
193
®
Intel
EP80579 Integrated Processor Product Line—Real Time Clock (RTC) Interface
Figure 130
Figure
129.
RTCX1
Internal
Oscillator
SUSCLK
shows the external circuitry that comprises the
EP80579
May 2010
Order Number: 320068-005US
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