
36
EPSON
S1C8F626 TECHNICAL MANUAL
5 PERIPHERAL CIRCUITS AND THEIR OPERATION (Oscillation Circuits and Operating Mode)
5.4.8 Programming notes
(1) When the high speed CPU operation is not
necessary, you should operate the peripheral
circuits according to the setting outline indicate
below.
CPU operating clock
OSC1
OSC3 oscillation circuit
OFF
(When the OSC3 clock is not necessary for
some peripheral circuits.)
(2) Since several tens of sec to several tens of msec
are necessary for the oscillation to stabilize after
turning the OSC3 oscillation circuit ON.
Consequently, you should switch the CPU
operating clock (OSC1
→ OSC3) after allowing
for a sufficient waiting time once the OSC3
oscillation goes ON. (The oscillation start time
will vary somewhat depending on the oscillator
and on the externally attached parts. Refer to
the oscillation start time example indicated in
Chapter 9, "ELECTRICAL CHARACTERIS-
TICS".)
(3) When switching the clock from OSC3 to OSC1,
be sure to switch OSC3 oscillation OFF with
separate instructions. Using a single instruction
to process simultaneously can cause a malfunc-
tion of the CPU.
(4)When switching the system clock from OSC3 to
OSC1 immediately after the power is turned on,
it is necessary to wait the OSC1 oscillation to
stabilize before the clock can be switched. The
OSC1 oscillation takes several tens of msec to
several seconds until it has completely stabilized.
(The oscillation start time will vary somewhat
depending on the oscillator and on the externally
attached parts. Refer to the oscillation start time
example indicated in Chapter 9, "ELECTRICAL
CHARACTERISTICS".)
(5) Before the Flash EEPROM can be programmed,
a maximum 5 msec of wait time is required for
the internal operating voltage to stabilize after
switching the operating mode. Also when
returning the IC to normal operation mode, be
sure to take this wait time before setting the
VDC register to "0".
(6) Setting the VDC register to "1" increases current
consumption. Be sure to reset the VDC register
to "0" after Flash EEPROM programming has
finished.