Epson S1C17624 Technical Manual page 277

25.4 Operating Modes
The R/F converter features three oscillation modes that use the RFC internal oscillator circuit and a mode for mea-
suring an external input clock. Also it includes a CR oscillation clock (RFCLK) monitoring function and continu-
ous oscillation function for measuring the oscillation clock frequency. Each channel can be set to a different mode.
25.4.1 Oscillation Mode
In measurements using the RFC internal oscillator circuit, operate the oscillator with the reference element and then
the sensor for the same duration in time to count each oscillation frequency. The sensor value can be determined
from the difference between the two count values by software. The R/F converter supports DC bias resistive or
capacitive sensors and AC bias resistive sensors. The RFC internal oscillator circuit can operate in three oscillation
modes corresponding to the sensor to be used that is specified by SMODE[1:0]/RFC_CTL register.
SMODe[1:0]
DC oscillation mode for measuring resistive sensors (SMODe[1:0] = 0x0, default)
This mode drives the oscillator with the reference resistor and resistive sensor by applying DC bias voltage.
Select this mode when a DC bias resistive sensor is connected. This mode enables two resistive sensors to be
connected to a channel. One reference resistor and one reference capacitor is also required.
SENBx
SENAx
Figure 25. 4.1.1 Connection Example in DC Oscillation Mode for Measuring Resistive Sensors
When one resistive sensor only is used, leave the unused pin open.
aC oscillation mode for measuring resistive sensors (SMODe[1:0] = 0x1)
This mode drives the oscillator with the reference resistor and resistive sensor by applying AC bias voltage. Se-
lect this mode when an AC bias resistive sensor is connected. This mode enables only one resistive sensor to be
connected to a channel. One reference resistor and one reference capacitor is also required.
Figure 25. 4.1.2 Connection Example in AC Oscillation Mode for Measuring Resistive Sensors
S1C17624/604/622/602/621 TeChniCal Manual
Table 25. 4.1.1 Oscillation Mode Selection
0x3 Reserved
0x2 DC oscillation mode for measuring capacitive sensors
0x1 AC oscillation mode for measuring resistive sensors
0x0 DC oscillation mode for measuring resistive sensors
R
R
SEN1
REFx
R
REF
RFINx
C
REF
SENBx
R
SEN
SENAx
REFx
RFINx
C
REF
Seiko epson Corporation
Oscillation mode
SEN2
Current passing direction
(DC driving)
R : Reference resistor
REF
R : Resistive sensor (DC bias)
SEN1
R : Resistive sensor (DC bias)
SEN2
C : Reference capacitor
REF
Current passing direction
(AC driving)
R
REF
R : Reference resistor
REF
R : Resistive sensor (AC bias)
SEN
C : Reference capacitor
REF
25 R/F COnVeRTeR (RFC)
(Default: 0x0)
25-3