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