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R/F converting operations
Reference oscillation
When the RFC_nTRG.SREF bit is set to 1 in Step 4 of the conversion procedure above, the RFC Ch.n
starts CR oscillation using the reference resistor. The measurement counter starts counting up
using the CR oscillation clock from the initial value that has been set. The time base counter starts
counting up using TCCLK from 0x000000.
When the measurement counter or the time base counter overflows (0xffffff → 0x000000), the
RFC_nTRG. SREF bit is cleared to 0 and the reference oscillation stops automatically.
The measurement counter overflow sets the RFC_nINTF.EREFIF bit to 1 indicating that the
reference oscillation has been terminated normally. If the RFC_nINTE.EREFIE bit = 1, a reference
oscillation completion interrupt request occurs at this point.
The time base counter overflow sets the RFC_nINTF.OVTCIF bit to 1 indicating that the reference
oscillation has been terminated abnormally. If the RFC_nINTE.OVTCIE bit = 1, a time base counter
overflow error interrupt request occurs at this point.
Sensor oscillation
When the RFC_nTRG.SSENA bit (sensor A) or the RFC_nTRG.SSENB bit (sensor B) is set to 1 in
Step 7 of the conversion procedure above, the RFC Ch.n starts CR oscillation using the sensor.
The measurement counter starts counting up using the CR oscillation clock from 0x000000. The
time base counter starts counting down using TCCLK from the value at the end of reference
oscillation.
When the time base counter reaches 0x000000 or the measurement counter overflows
(0xffffff →0x000000), the RFC_nTRG.SSENA bit or the RFC_nTRG.SSENB bit that started oscillation
is cleared to 0 and the sensor oscillation stops automatically.
The time base counter reaching 0x000000 sets the RFC_nINTF.ESENAIF bit (sensor A) or the
RFC_ nINTF.ESENBIF bit (sensor B) to 1 indicating that the sensor oscillation has been terminated
normally. If the RFC_nINTE.ESENAIE bit = 1 or the RFC_nINTE.ESENBIE bit = 1, a sensor A or sensor
B oscillation completion interrupt request occurs at this point.
The measurement counter overflow sets the RFC_nINTF.OVMCIF to 1 indicating that the sensor
oscillation has been terminated abnormally. If the RFC_nINTE.OVMCIE bit = 1, a measurement
counter overflow error interrupt request occurs at this point.
Max. count value
(0xffffff)
Initial value n
Measurement counter
0x000000 - n
Min. count value
(0x000000)
MC[23:0] = initial value (0x000000 - n)
Max. count value
(0xffffff)
Time base counter
Min. count value
(0x000000)
TC[23:0] = 0x000000
Figure 20.4.4.1 Counter Operations During Reference/Sensor Oscillation
Forced termination
20-6
Overflow
(normal termination)
EREFIF = 1, SREF = 0
Count up
Overflow
(error termination)
OVTCIF = 1, SREF = 0
Count up
Reference oscillation time tREF
SREF = 1
Start reference oscillation
Seiko Epson Corporation
Overflow
(error termination)
OVMCIF = 1, SSENx = 0
Count up
0x000000
(Automatically set by reference oscillation
or set via software)
(Automatically set by reference oscillation
or set via software)
Count down
Sensor oscillation time tSEN (= tREF)
SSENx = 1
Start sensor oscillation
S1C31D50 TECHNICAL MANUAL
Count value m1
Varies depending on
the environment
Count value m2
Calculate the sensor detecting
value from the measurement
counter value m1 and m2.
Time
Underflow
(normal termination)
ESENxIF = 1, SSENx = 0
Software settings
(Rev. 1.00)
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