18 R/F CONVERTER (RFC)
S1C17M20/M21/M22/M23/M24/M25
Seiko Epson Corporation
18-7
TECHNICAL MANUAL (Rev. 1.0)
Table 18.4.4.1 Error Factors
Error factor
Influence
External part tolerances
Large
Power supply voltage fluctuations
Large
Parasitic capacitance and resistance of the board
Middle
Temperature
Small
Unevenness of IC quality
Small
18.4.5 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 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 os-
cillation) 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.
RFINn pin
RFCLKOn pin
(RFCnCTL.RFCLKMD = 0)
RFCLKOn pin
(RFCnCTL.RFCLKMD = 1)
RFCnTRG.SSENA, SSENB, SREF
V
DD
V
SS
V
DD
V
SS
RFCnCTL.CONEN
Writing 1
Writing 0
Figure 18.4.5.1 CR Oscillation Clock (RFCLK) Waveform
18.5 Interrupts
The RFC has a function to generate the interrupts shown in Table 18.5.1.
Table 18.5.1 RFC Interrupt Function
Interrupt
Interrupt flag
Set condition
Clear
condition
Reference oscillation
completion
RFCnINTF.EREFIF
When reference oscillation has been completed normally
due to a measurement counter overflow
Writing 1
Sensor A oscillation
completion
RFCnINTF.ESENAIF When sensor A oscillation has been completed normally
due to the time base counter reaching 0x000000
Writing 1
Sensor B oscillation
completion
RFCnINTF.ESENBIF When sensor B oscillation has been completed normally
due to the time base counter reaching 0x000000
Writing 1
Measurement counter
overflow error
RFCnINTF.OVMCIF When sensor oscillation has been terminated abnormally
due to a measurement counter overflow
Writing 1
Time base counter
overflow error
RFCnINTF.OVTCIF
When reference oscillation has been terminated abnor-
mally due to a time base counter overflow
Writing 1
The RFC provides interrupt enable bits corresponding to each interrupt flag. An interrupt request is sent to the in-
terrupt controller only when the interrupt flag, of which interrupt has been enabled by the interrupt enable bit, is
set. For more information on interrupt control, refer to the “Interrupt Controller” chapter.