16 R/F COnVeRTeR
16-2
Seiko epson Corporation
S1C63003/004/008/016 TeChniCal Manual
(Rev. 1.1)
2.1 R/F converter clock frequencies
Table 16.
RFCKS[2:0]
RFC clock
7
f
OSC3
/ 4
6
f
OSC3
/ 2
5
f
OSC3
/ 1
4
Programmable timer 1
*
3
f
OSC1
/ 4 (8 kHz)
2
f
OSC1
/ 2 (16 kHz)
1
f
OSC1
/ 1 (32 kHz)
0
Off
f
OSC1
: OSC1 oscillation frequency. ( ) indicates the frequency when f
OSC1
= 32 kHz.
f
OSC3
: OSC3 oscillation frequency
When programmable timer 1* is selected, the programmable timer 1 underflow signal is divided by 2 before it is
used as the R/F converter clock. In this case, the programmable timer must be controlled before operating the serial
interface. Refer to the "Programmable Timer" chapter for controlling the programmable timer.
If it is not necessary to run the R/F converter, stop the clock supply by setting RFCKS[2:0] to "0" to reduce current
consumption.
* The programmable timer 1 output clock cannot be used in the S1C63003.
Connection Terminals and CR Oscillation Circuit
16.3
The R/F converter channel 0 input/output terminals and the RFOUT output terminal are shared with the I/O port
(P50–P53), and the terminal functions must be switched with software when using these terminals for the R/F con-
verter.
By setting the ERF[1:0] register to other than "0," P53, P52 and P51 are configured as the RFIN0, REF0 and SEN0
terminals, respectively.
The RFOUT output through the P50 port is effective when "1" is written to the RFOUT register. When the RFOUT
register is "0," P50 is used as an I/O port.
The table below lists the correspondence between the P50 to P53 terminals and the R/F converter input/output.
3.1 Setting input/output terminal functions
Table 16.
Terminal name
R/F converter input/output
P50
RFOUT
P51
SEN0
P52
REF0
P53
RFIN0
Note: At initial reset, P50 to P53 are configured as the I/O ports.
When using the R/F converter channel 0, switch the terminal functions (ERF[1:0] = "1," RFOUT =
"1") in the initialize routine.
Two systems of CR oscillation circuits, channel 0 and channel 1, are built into the R/F converter and perform CR
oscillation with the external resistor and capacitor.
The counter that is used to obtain R/F converted values is shared with channel 0 and channel 1. Therefore, operation
for two channels is realized by switching the CR oscillation circuit that performs R/F conversion. The channel to
perform R/F conversion and the sensor type should be selected using the ERF[1:0] register in advance.
3.2 Selecting channel and sensor type
Table 16.
ERF[1:0]
Channel and sensor type
3
Ch.1 DC
2
Ch.1 AC
1
Ch.0 DC
0
I/O
DC: R/F conversion using a DC bias resistive sensor such as a thermistor
AC: R/F conversion using an AC bias resistive sensor such as a humidity sensor