Nuvoton NuMicro ML51 Series, Technical Reference Manual, Page: 293 / 719

ML51/ML54/ML56
Sep. 01, 2020 Page 293 of 719 Rev 2.00
ML
51
/ML
54
/ML
5
6 S
E
RI
E
S
TECHNI
CA
L
RE
F
E
R
E
NC
E
M
A
NU
A
L
ML51/M
L54
/M
L56
Series
Tec
hnical Reference
Manual
OSC[2:0] as [1,0,x], LIRC will be selected as the system clock. Note that after the ML51/ML54/ML56
Series is powered, HIRC and LIRC will be both enabled and HIRC is default selected as the system
clock source. While using internal oscillators, X
IN
,
X
OUT
, X32
I
and X32
O
automatically switch as one
general purpose I/O to expend the number of general purpose I/O.
External Crystal/Resonator or Clock Input 6.2.1.3
There are three possible clock source options of external clock sources
– 4 R/W to 24 R/W high-speed
crystal/resonator (HXT), 32.768 R/W low-speed crystal/resonator (LXT), and the external clock input
(ECLK) through X
IN
pin. User can set OSC[2:0] as [0,1,x] to select ECLK as the system clock. By
setting OSC[2:0] as [1,1,0], HXT will be selected as the system clock. By setting OSC[2:0] as [1,1,1],
LXT will be selected as the system clock. When HXT or LXT is used as the system clock, X
IN
/ X32
IN
and X
OUT
/ X32
OUT
are the input and output, respectively, of an internal inverting amplifier. A crystal or
resonator should be connected between X
IN
/ X32
IN
and X
OUT
/X32
O
UT
pins. When enabling and
selecting ECLK as the system clock source, the system clock is supplied via the X
IN
pin. The common
application is to drive X
IN
with an active oscillator or clocks from another host device. Be aware that
user should never feed any clock signal larger than voltage 1.8V to X
IN
and give a DC voltage to X
OUT
pin which value is half of X
IN
, when ECLK mode is selected. Otherwise, it may break the device.