Epson S1C17624 Technical Manual page 275

25 R/F Converter (RFC)
25.1 RFC Module Overview
The S1C17624/604/622/602/621 includes an R/F converter (RFC) module with two conversion channels. It is ca-
pable of being used as a CR oscillation type A/D converter. A thermo-hygrometer can easily be implemented by
connecting only resistive or capacitive sensors (e.g., thermistor and humidity sensor) and a few passive elements
(resistors and capacitors) to the R/F converter.
The following shows the features of the RFC module:
• Conversion method:
• Number of conversion channels:
• Oscillation mode:
• Counter length:
• Five types of interrupts can be generated: Reference oscillation completion interrupt
Figure 25.1.1 shows the RFC configuration.
HSCLK
OSC1
RFCLKO
SENB0
SENA0
REF0
RFIN0
RFIN1
REF1
SENA1
SENB1
The R/F converter converts the resistance or capacitance of the sensor connected into frequency (RFCLK) using the
embedded CR oscillator circuit, and counts this frequency using the measurement counter for a set period of time
to provide the digital value equivalent to the sensor value. The time base counter is also included for generating
the measurement time by counting an internal clock (TCCLK). In addition to CR oscillation using a sensor (sensor
oscillation), the R/F converter performs CR oscillation using a reference element with less variation in the charac-
teristics due to external factors (reference oscillation). This removes error factors such as voltage fluctuations and
unevenness in quality to realize precise measurements. The CR oscillator circuit supports AC driving and external
clock input as well as general DC driving, allowing use of various sensors.
S1C17624/604/622/602/621 TeChniCal Manual
Resistance to frequency conversion type
Max. 2 channels
DC oscillation mode (for resistive sensors)
AC oscillation mode (for resistive sensors)
DC oscillation mode (for capacitive sensors)
24 bits
Sensor A oscillation completion interrupt
Sensor B oscillation completion interrupt
Measurement counter overflow error interrupt
Time base counter overflow error interrupt
Divider
(1/1–1/8)
Gate
Ch.0
oscillator
circuit
Multi-
plexer
CR
Ch.1
oscillation
oscillator
control
circuit
circuit
Figure 25. 1.1 R/F Converter Configuration
Seiko epson Corporation
TCCLK
Time base counter
TC[23:0]
RFCLK Measurement counter
MC[23:0]
25 R/F COnVeRTeR (RFC)
To ITC
Interrupt
control
circuit
Counter
control
circuit
RFC
25-1