
S1C88348/317/316/308 TECHNICAL HARDWARE
EPSON
I-65
5 PERIPHERAL CIRCUITS AND THEIR OPERATION (Output Ports)
s FOUT output (R34)
In order for the S1C883xx to provide clock signal to
an external device, a FOUT signal (oscillation clock
fOSC1 or fOSC3 dividing clock) can be output from
the output port terminal R34.
Figure 5.6.5.5 shows the configuration of output
port R34.
Since the FOUT signal is generated asynchronously
from the register FOUTON, when the signal is
turned ON or OFF by the register settings, a hazard
of a 1/2 cycle or less is generated.
Figure 5.6.5.6 shows the output waveform of the
FOUT signal.
Register R34D
Register FOUTON
R34 output
FOUT signal
Fig. 5.6.5.5 Configuration of R34
The output control for the FOUT signal is done by
the register FOUTON. When you set "1" for the
FOUTON, the FOUT signal is output from the
output port terminal R34, when "0" is set, the HIGH
(VDD) level is output. At this time, "1" must always
be set for the data register R34D.
The frequency of the FOUT signal can be selected in
software by setting the registers FOUT0–FOUT2.
The frequency is selected any one from among
eight settings as shown in Table 5.6.5.3.
Table 5.6.5.3 FOUT frequency setting
When the FOUT frequency is made "fOSC3/n", you
must turn on the OSC3 oscillation circuit before
outputting FOUT. A time interval of several msec to
several 10 msec, from the turning ON of the OSC3
oscillation circuit to until the oscillation stabilizes, is
necessary, due to the oscillation element that is used.
Consequently, if an abnormality occurs as the result
of an unstable FOUT signal being output externally,
you should allow an adequate waiting time after
turning ON of the OSC3 oscillation, before turning
outputting FOUT. (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 7, "ELEC-
TRICAL CHARACTERISTICS".)
At initial reset, OSC3 oscillation circuit is set to OFF
state.
FOUTON
FOUT output (R34)
01
Fig. 5.6.5.6 Output waveform of FOUT signal
s BZ output (R50)
In order for the S1C883xx to drive an external
buzzer, a BZ signal (sound generator output) can be
output from the output port terminal R50.
The configuration of the output port R50 is shown
in Figure 5.6.5.7.
BZON/BZSHT
BZ output (R50)
01
Fig. 5.6.5.7 Configuration of R50
The output control for the BZ signal is done by the
registers BZON, BZSHT and BZSTP. When you set
"1" for the BZON or BZSHT, the BZ signal is output
from the output port terminal R50, when "0" is set
for the BZON or "1" is set for the BZSTP, the LOW
(VSS) level is output. At this time, "0" must always
be set for the data register R50D.
The BZ signal which is output makes use of the
output of the sound generator. With respect to
control of frequency and envelope, see "5.13 Sound
Generator".
Since the BZ signal is generated asynchronously
from the registers BZON, BZSHT and BZSTP, when
the signal is turned ON or OFF by the register
settings, a hazard of a 1/2 cycle or less is generated.
Figure 5.6.5.8 shows the output waveform of the BZ
signal.
Fig. 5.6.5.8 Output waveform of BZ signal
Register BZSTP
Register BZON
Register BZSHT
R
SQ
One-shot time up
R50 output
BZ signal
Register R50D
FOUT2
FOUT frequency
0
1
fOSC1 / 1
fOSC1 / 2
fOSC1 / 4
fOSC1 / 8
fOSC3 / 1
fOSC3 / 2
fOSC3 / 4
fOSC3 / 8
FOUT1
0
1
0
1
FOUT0
0
1
0
1
0
1
0
1
fOSC1:
fOSC3:
OSC1 oscillation frequency
OSC3 oscillation frequency