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S1C88650 TECHNICAL MANUAL EPSON 63
5 PERIPHERAL CIRCUITS AND THEIR OPERATION (Serial Interface)
This register setting is invalid in clock synchronous
slave mode and the external clock input from the
_________
SCLK terminal is used.
When the "programmable timer" is selected, the
programmable timer 1 underflow signal is divided
by 2 and this signal is used as the clock source.
With respect to the transfer rate setting, see "5.10
Programmable Timer".
At initial reset, the synchronous clock is set to
"f
OSC3
/16".
Whichever clock is selected, the signal is further
divided by 16 and then used as the synchronous
clock.
Furthermore, external clock input is used as is for
_________
SCLK in clock synchronous slave mode.
Table 5.8.4.2 shows an examples of transfer rates and
OSC3 oscillation frequencies when the clock source
is set to programmable timer.
When the demultiplied signal of the OSC3 oscilla-
tion circuit is made the clock source, it is necessary
to turn the OSC3 oscillation ON, prior to using the
serial interface.
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,
you should allow an adequate waiting time after
turning ON of the OSC3 oscillation, before starting
transmitting/receiving of serial interface. (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".)
At initial reset, the OSC3 oscillation circuit is set to
ON status.
Transfer rate
(bps)
19,200
9,600
4,800
2,400
1,200
600
300
150
PST1X
00H
00H
00H
00H
00H
00H
02H
02H
RDR1X
03H
07H
0FH
1FH
3FH
7FH
1FH
3FH
PST1X
00H
00H
00H
00H
00H
00H
03H
03H
RDR1X
04H
09H
13H
27H
4FH
9FH
09H
13H
PST1X
00H
00H
00H
00H
00H
00H
01H
02H
RDR1X
05H
0BH
17H
2FH
5FH
BFH
BFH
5FH
f
OSC3
= 2.4756 MHz f
OSC3
= 3.0720 MHz f
OSC3
= 3.6864 MHz
OSC3 oscillation frequency / Programmable timer settings
Table 5.8.4.2 OSC3 oscillation frequencies and transfer rates
Data input
Data output
CLOCK output
READY input
SIN(P10)
SOUT(P11)
SCLK(P12)
SRDY(P13)
External
serial device
S1C88650
Data input
Data output
CLOCK input
READY output
SIN(P10)
SOUT(P11)
SCLK(P12)
Input port(Kxx)
External
serial device
S1C88650
(a) Clock synchronous master mode
(b) Clock synchronous slave mode
(c) Asynchronous 7-bit/8-bit mode
Fig. 5.8.3.1 Connection examples of serial interface I/O terminals
5.8.4 Clock source
There are four clock sources and selection is made
by setting the two bits of the clock source selection
register SCS0 and SCS1 as shown in table below.
Table 5.8.4.1 Clock source
SCS1
1
1
0
0
SCS0
1
0
1
0
Clock source
Programmable timer
f
OSC3 / 4
fOSC3 / 8
f
OSC3 / 16
Data input
Data output
SIN(P10)
SOUT(P11)
External
serial device
S1C88650
f
OSC3
1/4
1/8
1/16
1/16
Synchro-
nous clock
Programmable timer 1
underflow signal
SCLK
(Clock synchronous slave mode)
Divider Selector Selector
1/2
OSC3
oscillation
circuit
Fig. 5.8.4.1
Division of the synchronous clock
∗ Since the underflow signal only is used as the clock source, the
CDR1X register value does not affect the transfer rates.