
I-36
EPSON
S1C621A0 TECHNICAL HARDWARE
CHAPTER 3: PERIPHERAL CIRCUITS (Remote LED Control)
The S1C621A0 supports the following functions to imple-
ment remote-controlled transmission:
A carrier frequency(fcarrier) can be set to a frequency 1/8
or 1/12 times the ceramic oscillator frequency (OSC3) by
software. (division ratio 1)
Note
If an option is selected without use of OSC3, the OSC1 clock
(instead of the OSC3 clock) is introduced into the REM circuit.
For an option selected without using OSC3, the term "OSC3"
should read "OSC1" in the description that follows.
A carrier duty can be selected by software from the four
different values.
Software supports two timer control modes: named soft-
timer mode and hard-timer mode. In the soft-timer mode
(software timer control mode), the ON/OFF timing of
carriers is controlled by software. In the hard-timer mode
(hardware timer control mode), software sets the ON-time,
then hardware generates a waveform and an interrupt
(REM interrupt) each time one bit is transmitted.
Table 3.9.1 summarizes the differences between the soft-
timer mode and the hard-timer mode.
Table 3.9.1
Characteristics of Soft-timer
and Hard-timer Control Modes
Processing of other
routines during REM
output
Reference cycle ( )
sway during REM
transmission
Setting of REM
output width
Relation between REM
reference cycle and
moduration frequency
cycle
Carrier waveform
Difficult
Source oscillation
sway and errors
caused by instruction
cycles
Variable to
any width
Variable
Duty slightly
disturbed before
and after ON time
Possible
Source oscillation
sway only
Fixed to
several width
Fixed to
several cycles
Stabilized at
setting
Item
Soft-timer mode
Hard-timer mode
τ