Dd Ss - Epson S1C17624 Technical Manual

25 R/F COnVeRTeR (RFC)
DC oscillation mode for measuring capacitive sensors (SMODe[1:0] = 0x2)
This mode drives the oscillator with the reference capacitor and capacitive sensor by applying DC bias voltage.
Select this mode when a DC bias capacitive sensor is connected. This mode enables only one capacitive sensor
to be connected to a channel. One reference resistor and one reference capacitor is also required.
Figure 25. 4.1.3 Connection Example in DC Oscillation Mode for Measuring Capacitive Sensors
25.4.2 external Clock input Mode (event Counter Mode)
This mode enables to input clocks/pulses from an external circuit such as an oscillator and count them same as
those of internal oscillation clocks. It supports rectangular waves, triangular waves, and sign waves to be input. (For
the threshold voltage of the Schmitt input buffer, see "Electrical Characteristics.")
Setting EVTEN/RFC_CTL register to 1 enables this function. The measurement control procedure is the same as
that when the internal oscillator circuit is used.
The unused pins should be left open.
25.4.3 Functions for Measuring CR Oscillation Clock Frequency
CR Oscillation Clock (RFClK) Monitoring Function
The CR oscillation clock (RFCLK) during converting can be output from the RFCLKO pin for monitoring. Use
this output to measure the oscillation frequency.
SSENA, SSENB, or SREF
(Measurement counter clock)
Continuous oscillation function
The CR oscillations by the sensor and reference element will automatically stop due to stop conditions. Setting
1 to CONEN/RFC_CTL register enables the continuous oscillation function and CR oscillation will continue
until stopped by software. Using this function with the CR oscillation monitoring function helps easily measure
the CR oscillation clock frequency.
25-4
SENBx
SENAx
C
SEN
REFx
R
REF
RFINx
SENBx
SENAx
REFx
RFINx
Figure 25. 4.2.1 External Clock Input
RFINx pin
RFCLKO output
Figure 25. 4.3.1 CR Oscillation Clock (RFCLK) Waveform
Seiko epson Corporation
C
REF
Current passing direction
(DC driving)
R : Reference resistor
REF
C : Capacitive sensor
SEN
C : Reference capacitor
REF
Supports rectangular waves,
triangular waves, and sign waves.
S1C17624/604/622/602/621 TeChniCal Manual
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