Epson S1C88650 - Manual (Page 64)

56 EPSON S1C88650 TECHNICAL MANUAL
5 PERIPHERAL CIRCUITS AND THEIR OPERATION (I/O Ports)
■ FOUT output (P16)
In order for the S1C88650 to provide clock signal to
an external device, a FOUT signal (oscillation clock
f
OSC1 or f OSC3 dividing clock) can be output from
the P16 port terminal.
The output control for the FOUT signal is done by
the register FOUTON. When FOUTON is set to "1",
the FOUT signal is output from the P16 port
terminal, when "0" is set, the port is set for DC
output. When FOUTON is "1", settings of the I/O
control register IOC16 and data register P16D
become invalid.
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 5.7.5.2.
Table 5.7.5.2 FOUT frequency setting
FOUT2 FOUT frequency
1
1
1
1
0
0
0
0
f OSC3 / 8
f OSC3 / 4
f OSC3 / 2
f OSC3 / 1
f OSC1 / 8
f OSC1 / 4
f OSC1 / 2
f OSC1 / 1
FOUT1
1
1
0
0
1
1
0
0
FOUT0
1
0
1
0
1
0
1
0
f OSC1 :
f OSC3 :
OSC1 oscillation frequency
OSC3 oscillation frequency
When the FOUT frequency is made "f OSC3 /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 abnormal-
ity 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 8, "ELECTRICAL
CHARACTERISTICS".)
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 5.7.5.2 shows the output waveform of the
FOUT signal.
FOUTON
FOUT output
(P16)
0 1
Fig. 5.7.5.2 Output waveform of FOUT signal
■ Inverted TOUT output (P17)
The S1C88650 provides an output of the TOUT2 or
TOUT3 inverted signal (programmable timer
output clock) to supply a clock to external devices
or to drive a buzzer.
By using this output with the TOUT2 or TOUT3
output from the P15 terminal, the bias level to be
applied to the buzzer can be increased.
___________
The output control for the TOUTx signals (x = 2 or
3) is done by the registers RPTOUTx. When
___________
RPTOUTx is set to "1", the TOUTx signal is output
from the P17 port terminal, when "0" is set, the port
is set for DC output. When RPTOUTx is "1",
settings of the I/O control register IOC17 and data
register P17D become invalid.
___________ ___________
The TOUT2 and TOUT3 signals are generated from
the underflow and compare-match signals of the
programmable timers 2 and 3.
With respect to frequency control, see "5.10 Pro-
grammable Timer".
___________
Since the TOUTx signals are generated asynchro-
nously from the registers RPTOUTx, when the
signals are turned ON or OFF by the register
settings, a hazard of a 1/2 cycle or less is generated.
Figure 5.7.5.3 shows the output waveform of the
_________
TOUT signal.
RPTOUTx
TOUTx output
(P17)
0 1
________
Fig. 5.7.5.3 Output waveform of TOUT signal
Note: If RPTOUT2 and RPTOUT3 are set to "1" at
the same time, RPTOUT3 is effective.