RL78/D1A User's Manual: Hardware - Renesas

Under development
Preliminary document
Specifications in this document are tentative and subject to change.
RL78/D1A CHAPTER 25 SAFETY FUNCTIONS
25.3.7 Frequency detection function
The IEC60730 standard mandates checking that the oscillation frequency is correct.
The frequency detection function can detect whether the clock is operating on an abnormal frequency by comparing the
high-speed on-chip oscillator clock or external X1 oscillation clock with the low-speed on-chip oscillator clock (15 kHz).
X1
X2
TI05
Figure 25-13. Configuration of Frequency Detection Function
High-speed on-chip
oscillator (f IH)
X1 oscillator
(f MX)
Low-speed on-chip
oscillator
(15 kHz)
f IL
Watchdog timer
(WDT)
Timer array unit 0
(TAU0)
Whether the clock frequency is correct or not can be judged by measuring the pulse width under the following
conditions:
● The high-speed on-chip oscillator clock (fIH) or the external X1 oscillation clock (fMX) is selected as the
CPU/peripheral hardware clock (fCLK).
● The low-speed on-chip oscillator clock (fIL:15kHz) is selected as the timer input for channel 5 of timer array unit 0
(TAU0).
If pulse width measurement results in an abnormal value, it can be concluded that the clock frequency is abnormal.
For how to execute pulse width measurement, see 6.7.4 Operation as input pulse interval measurement.
R01UH0317EJ0004 Rev. 0.04 1147
Feb. 22, 2013
Selector Selector
fCLK