
S1C88409 TECHNICAL MANUAL
EPSON
67
CHAPTER 5: PERIPHERAL CIRCUITS AND OPERATION (Prescaler and Clock Control Circuit)
PRFO3: FOUT3 output control register
(00FF14HD3)
Controls the FOUT3 output.
When "1" is written: ON
When "0" is written: OFF
Reading: Valid
When "1" is written to the PRFO3 register, the
FOUT3 (R40) terminal outputs the clock selected
with the PSF3 register. However, the high-imped-
ance control register HZR40 of the output port R40
must be set to "0" and the data register R40D must
be set to "1".
When "0" is written, the clock is not output.
At initial reset, the PRFO3 register is set to "0"
(OFF).
PSTP0–PSTP2: Touch panel controller clock
division ratio selection register (00FF16HD0–D2)
Selects the clock for the touch panel controller.
It can be selected from 5 types of division ratio as
shown in Table 5.5.5.1(b).
This register can also be read.
At initial reset, the PSTP register is set to "0"
(fOSC3/1).
PRTP: Touch panel controller clock control
register (00FF16HD3)
Controls the clock supply of the touch panel
controller.
When "1" is written: ON
When "0" is written: OFF
Reading: Valid
By writing "1" to the PRTP register, the clock that is
selected with the PSTP register is output to the
touch panel controller.
When "0" is written, the clock is not output.
At initial reset, the PRTP register is set to "0" (OFF).
5.5.6 Programming note
When using an output clock from the OSC3
prescaler, it is necessary to turn the OSC3 oscilla-
tion circuit on. Furthermore, the OSC3 oscillation
circuit takes a maximum 20 msec for stabilizing
oscillation after turning the OSC3 oscillation
circuit on. Therefore, wait a long enough interval
after the OSC3 oscillation goes on before turning
the clock output of the OSC3 prescaler on. (The
oscillation start time varies depending on the
oscillator and external components to be used.
Refer to Chapter 8, "ELECTRICAL CHARACTER-
ISTICS", in which an example of oscillation start
time is indicated.)