F Converter (Rfc); Overview - Epson S1C17M20 Technical Manual

18 R/F Converter (RFC)

18.1 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 18.1.1 shows the RFC configuration.
Table 18.1.1 RFC Channel Configuration of S1C17M20/M21/M22/M23/M24/M25
Item
24-pin package
Number of channels
RFC Ch.n
Interrupt
controller
OVTCIE
OVMCIE
ESENBIE
ESENAIE
EREFIE
TCCLK
CLKSRC[1:0]
Clock generator
CLKDIV[1:0]
DBRUN
MODEN
CONEN
EVTEN
SMODE[1:0]
S1C17M20/M21/M22/M23/M24/M25
TECHNICAL MANUAL (Rev. 1.0)
S1C17M20/M23
S1C17M21/M24
32-pin package
–
OVTCIF
Interrupt OVMCIF
control circuit ESENBIF
ESENAIF
EREFIF
Time base counter
Counter
control circuit
Measurement counter
CR oscillation
control circuit
Figure 18.1.1 RFC Configuration
Seiko Epson Corporation
18 R/F CONVERTER (RFC)
(Note: See the table below.)
S1C17M22/M25
2 channels (Ch.0 and Ch.1)
* Can only be used in DC oscillation mode
for resistive sensor measurements.
RFCLKMD
TC[23:0]
1/2
MC[23:0]
SSENB
SSENA Oscillation
SREF circuit
RFCLKOn
RFINn
REFn
SENAn
SENBn
18-1