The real-time clock (RTC) is located in the always-on domain, and is clocked by a selectable
low-frequency clock source. For best accuracy, the RTC should be driven by an external
32.768 kHz watch crystal oscillator, but to reduce system cost, can be driven by a factory-
trimmed on-chip oscillator.
r t ccmp
r t chi
r t ccf g
A
O
N
T
ile
L
in
k
r t ccmpi p
l f cl k
aonr st
r t cl o
r t cs
r t cen
r t cscal e
>=?
Figure 8:
Real-Time Clock
The real-time counter is based around the
rtccounthi
/
rtccountlo
register pair, which incre-
ment at the low-frequency clock rate when the RTC is enabled. The
rtccountlo
register holds
the low 32 bits of the RTC, while
rtccounthi
holds the upper 16 bits of the RTC value. The
total ≥48-bit counter width ensures there will no counter rollover for over 270 years assuming a
32.768 kHz low-frequency real-time clock source. The counter registers can be read or written
over the TileLink bus.
FE310-G003 Manual
© SiFive, Inc.
Page 72
Содержание FE310-G003
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