20-7
Seiko Epson Corporation
S1C31D50 TECHNICAL MANUAL
(Rev. 1.00)
To abort reference oscillation or sensor oscillation, write 0 to the RFC_
n
TRG.SREF bit (reference
oscillation), the RFC_
n
TRG.SSENA bit (sensor A oscillation), or the RFC_
n
TRG.SSENB bit (sensor B
oscillation) used to start the oscillation. The counters maintain the value at the point they stopped,
note, however, that the conversion results cannot be guaranteed if the oscillation is resumed. When
resuming oscillation, execute from counter initialization again.
Conversion error
Performing reference oscillation and sensor oscillation with the same resistor and capacitor results
n
≈
m. The difference between n and m is a conversion error. Table 20.4.4.1 lists the error factors.
(n: measurement counter initial value, m: measurement counter value at the end of sensor
oscillation)
Table 20.4.4.1 Error Factors
Error factor
Influence
External part tolerances
Large
Power supply voltage
fl
uctuations
Large
Parasitic capacitance and resistance of the board
Middle
Temperature
Small
Unevenness of IC quality
Small
20.4.5.
CR Oscillation Frequency Monitoring Function
The CR oscillation clock (RFCLK) generated during converting operation can be output from the
RFCLKO
n
pin for monitoring. By setting the RFC_
n
CTL.CONEN bit to 1, the RFC Ch.
n
enters continuous
oscillation mode that disables oscillation stop conditions to continue oscillating operations. In this case,
set the RFC_
n
TRG.SREF bit (reference oscillation), the RFC_
n
TRG.SSENA bit (sensor A oscillation), or the
RFC_
n
TRG.SSENB bit (sensor B oscillation) to 1 to start oscillation. Set the bit to 0 to stop oscillation.
Using this function helps easily measure the CR oscillation clock frequency. Furthermore, setting the
RFC_
n
CTL.RFCLKMD bit to 1 changes the output clock to the divided-by-two RFCLK clock.
Figure 20.4.5.1 CR Oscillation Clock (RFCLK) Waveform
RFC_
n
CTL.CONEN
RFC_
n
TRG.SSENA, SSENB, SREF
RFIN
n
pin
RFCLKO
n
pin
(RFC_
n
CTL.RFCLKMD = 0)
RFCLKO
n
pin
(RFC_
n
CTL.RFCLKMD = 1)
Writing 1
Writing 0
V
DD
V
SS
V
DD
V
SS
Summary of Contents for S1C31D50
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