25 R/F COnVeRTeR (RFC)
S1C17624/604/622/602/621 TeChniCal Manual
Seiko epson Corporation
25-1
R/F Converter (RFC)
25
RFC Module Overview
25.1
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:
Resistance to frequency conversion type
• Number of conversion channels:
Max. 2 channels
• Oscillation mode:
DC oscillation mode (for resistive sensors)
AC oscillation mode (for resistive sensors)
DC oscillation mode (for capacitive sensors)
• Counter length:
24 bits
• Five types of interrupts can be generated: Reference oscillation completion interrupt
Sensor A oscillation completion interrupt
Sensor B oscillation completion interrupt
Measurement counter overflow error interrupt
Time base counter overflow error interrupt
Figure 25.1.1 shows the RFC configuration.
To ITC
RFCLK
RFCLKO
SENB0
SENA0
REF0
RFIN0
RFIN1
REF1
SENA1
SENB1
Multi-
plexer
Ch.0
oscillator
circuit
Counter
control
circuit
Ch.1
oscillator
circuit
CR
oscillation
control
circuit
Measurement counter
MC[23:0]
Internal data bus
HSCLK
OSC1
Divider
(1/1–1/8)
RFC
Time base counter
TC[23:0]
Interrupt
control
circuit
Gate
TCCLK
1.1 R/F Converter Configuration
Figure 25.
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.