Renesas RL78/G1P Hardware User Manual page 674

RL78/G1P
20.9 Frequency detection function
The IEC60730 standard mandates checking that the oscillation frequency is correct.
By using the CPU/peripheral hardware clock frequency (f
channel 1 of the timer array unit 0 (TAU0), whether the proportional relationship between the two clock frequencies is
correct can be determined. Note that, however, if one or both clock operations are completely stopped, the proportional
relationship between the clocks cannot be determined.
X1
X2
TI01
Low-speed on-chip
oscillator
(15 kHz (TYP.))
<Operational overview>
Whether the clock frequency is correct or not can be judged by measuring the pulse interval under the following
conditions:
 The internal high-speed oscillation clock (f
CPU/peripheral hardware clock (f
 The internal low-speed oscillation clock (f
(TAU0).
If pulse interval measurement results in an abnormal value, it can be concluded that the clock frequency is abnormal.
For how to execute pulse interval measurement, see 6.8.3 Operation as input pulse interval measurement.
R01UH0895EJ0100 Rev.1.00
Nov 29, 2019
Figure 20-13. Configuration of Frequency Detection Function
High-speed on-chip
oscillator (f )
IH
X1 oscillator
(f )
MX
f
IL
).
CLK
15 kHz) is selected as the timer input for channel 1 of timer array unit 0
IL:
CHAPTER 20 SAFETY FUNCTIONS
) and measuring the pulse width of the input signal to
CLK
Watchdog timer
(WDT)
) or the external X1 oscillation clock (f
IH
f
CLK
<1>
Channel 1 of timer
<2>
array unit 0
(TAU0)
) is selected as the
MX
655