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21 R/F Converter (RFC)
21.1 Overview
The RFC is a CR oscillation type A/D converter (R/F converter).
The features of the RFC are listed below.
• Converts the sensor resistance into a digital value by performing CR oscillation and counting the oscillation
clock.
• Achieves high-precision measurement system with low errors by oscillating the reference resistor and the sensor
in the same conditions to obtain the difference between them.
• Includes a 24-bit measurement counter to count the oscillation clocks.
• Includes a 24-bit time base counter to count the internal clock for equalizing the measurement time between the
reference resistor and the sensor.
• Supports DC bias resistive sensors and AC bias resistive sensors.
(A thermometer/hygrometer can be easily implemented by connecting a thermistor or a humidity sensor and a
few passive elements (resistor and capacitor).)
• Allows measurement (counting) by inputting external clocks.
• Provides an output and continuous oscillation function for monitoring the oscillation frequency.
• Can generate reference oscillation completion, sensor (A and B) oscillation completion, measurement counter
overflow error, and time base counter overflow error interrupts.
Figure 21.1.1 shows the RFC configuration.
Item
Number of channels
RFC Ch.n
CPU
OVTCIE
OVMCIE
ESENBIE
ESENAIE
EREFIE
TCCLK
CLKSRC[1:0]
Clock generator
CLKDIV[1:0]
DBRUN
MODEN
CONEN
EVTEN
SMODE[1:0]
S1C31D41 TECHNICAL MANUAL
(Rev. 1.1)
Table 21.1.1 RFC Channel Configuration of S1C31D41
32-pin package
–
Interrupt
control circuit
ESENBIF
ESENAIF
Counter
control circuit
Measurement counter
CR oscillation
control circuit
Figure 21.1.1 RFC Configuration
Seiko Epson Corporation
(Note: See the table below.)
48-pin package
1 channel (Ch.0)
Note: DC oscillation mode for resistive sensor
measurements can only be used.
OVTCIF
OVMCIF
EREFIF
Time base counter
TC[23:0]
MC[23:0]
SSENB
SSENA
Oscillation
SREF
21 R/F CONVERTER (RFC)
64-pin package
RFCLKMD
1/2
RFCLKOn
RFINn
REFn
circuit
SENAn
SENBn
21-1
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