PFS122
8bit MTP MCU with 12-bit R-Type ADC
resonator, please refer to its specification for proper values of C1 and C2.
Measured
Start-up time
6ms
Frequency
C1
C2
Conditions
4MHz
1MHz
32KHz
4.7pF
10pF
22pF
4.7pF
10pF
22pF
(eoscr[6:5]=11, misc.6=0)
(eoscr[6:5]=10, misc.6=0)
(eoscr[6:5]=01, misc.6=0)
11ms
450ms
Table 4: Recommend values of C1 and C2 for crystal and resonator oscillators
When using the crystal oscillator, user must pay attention to the stable time of oscillator after enabling it, the
stable time of oscillator will depend on frequency “crystal type” external capacitor and supply voltage. Before
switching the system to the crystal oscillator, user must make sure the oscillator is stable; the reference
program is shown as below:
void
{
FPPA0 (void)
. ADJUST_IC SYSCLK=IHRC/16, IHRC=16MHz, VDD=5V
$
$
EOSCR
Enable, 4MHz;
// EOSCR = 0b110_00000;
T16M EOSC, /1, BIT13;
// T16 receive 2^14=16384 clocks of crystal EOSC,
// Intrq.T16 =>1, crystal EOSC Is stable
WORD
count =
0;
stt16 count;
Intrq.T16
=
0;
do
{
nop; }while(!Intrq.T16);
// count from 0x0000 to 0x2000, then set INTRQ.T16
// switch system clock to EOSC;
clkmd=
0xB4;
Clkmd.4 = 0;
...
// disable IHRC
Please notice that the crystal oscillator should be fully turned off before entering the power-down mode, in
order to avoid unexpected wake-up event.
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PDK-DS-PFS122-EN_V000-May 28, 2020
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