20 R/F CONVERTER (RFC)
S1C31D50/D51 TECHNICAL MANUAL
Seiko Epson Corporation
20-7
(Rev. 2.00)
Table 20.4.4.1 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
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 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.
RFINn pin
RFCLKOn pin
(RFC_nCTL.RFCLKMD = 0)
RFCLKOn pin
(RFC_nCTL.RFCLKMD = 1)
RFC_nTRG.SSENA, SSENB, SREF
V
DD
V
SS
V
DD
V
SS
RFC_nCTL.CONEN
Writing 1
Writing 0
Figure 20.4.5.1 CR Oscillation Clock (RFCLK) Waveform
20.5 Interrupts
The RFC has a function to generate the interrupts shown in Table 20.5.1.
Table 20.5.1 RFC Interrupt Function
Interrupt
Interrupt flag
Set condition
Clear
condition
Reference oscillation
completion
RFC_nINTF.EREFIF When reference oscillation has been completed normally
due to a measurement counter overflow
Writing 1
Sensor A oscillation
completion
RFC_nINTF.ESENAIF When sensor A oscillation has been completed normally
due to the time base counter reaching 0x000000
Writing 1
Sensor B oscillation
completion
RFC_nINTF.ESENBIF When sensor B oscillation has been completed normally
due to the time base counter reaching 0x000000
Writing 1
Measurement counter
overflow error
RFC_nINTF.OVMCIF When sensor oscillation has been terminated abnormally
due to a measurement counter overflow
Writing 1
Time base counter
overflow error
RFC_nINTF.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 CPU
core 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” chapter.