
54
EPSON
S1C8F626 TECHNICAL MANUAL
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
_________
SCLKx terminal is used.
When the "programmable timer" is selected, the
programmable timer 1 (Ch.0) or timer 7 (Ch.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
"fOSC3/16".
Whichever clock is selected, the signal is further
divided by 16 and then used as the synchronous
clock and the sampling clock.
Furthermore, external clock input is used as is for
_________
SCLKx in clock synchronous slave mode.
Table 5.7.4.2 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 tens of sec to several
tens of 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 oscilla-
tion, 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 9, "ELEC-
TRICAL CHARACTERISTICS".)
At initial reset, the OSC3 oscillation circuit is set to
OFF status.
Fig. 5.7.4.1 Division of the synchronous clock
fOSC3
TCLK
1/4
1/8
1/16
Synchronous/
sampling clock
SCLKx
(Clock synchronous slave mode)
Divider
Selector
1/2
Programmable timer
underflow signal
(Ch.0: timer 1, Ch.1: timer 7)
OSC3
oscillation
circuit
Data input
Data output
CLOCK input
READY output
SINx(P10/P20)
SOUTx(P11/P21)
SCLKx(P12/P22)
Input port(K0x)
External
serial device
S1C8F626
(a) Clock synchronous master mode
Data input
Data output
CLOCK output
READY input
External
serial device
SINx(P10/P20)
SOUTx(P11/P21)
SCLKx(P12/P22)
SRDYx(P13/P23)
S1C8F626
(b) Clock synchronous slave mode
Data input
Data output
SINx(P10/P20)
SOUTx(P11/P21)
External
serial device
S1C8F626
(c) Asynchronous 7-bit/8-bit mode
Fig. 5.7.3.1 Connection examples of serial interface I/O terminals
5.7.4 Clock source
There are four clock sources and selection is made
by setting the two bits of the clock source selection
register SCSx0 and SCSx1 as shown in table below.
Table 5.7.4.1 Clock source
SCSx1
1
0
SCSx0
1
0
1
0
Clock source
Programmable timer 1 (Ch.0)
Programmable timer 7 (Ch.1)
fOSC3 / 4
fOSC3 / 8
fOSC3 / 16
Table 5.7.4.2 OSC3 oscillation frequencies and transfer rates
Transfer rate
(bps)
19,200
9,600
4,800
2,400
1,200
600
300
150
PST1x/7x
00H
02H
RDR1x/7x
03H
07H
0FH
1FH
3FH
7FH
1FH
3FH
PST1x/7x
00H
03H
RDR1x/7x
04H
09H
13H
27H
4FH
9FH
09H
13H
PST1x/7x
00H
01H
02H
RDR1x/7x
05H
0BH
17H
2FH
5FH
BFH
5FH
fOSC3 = 2.4576 MHz
fOSC3 = 3.0720 MHz
fOSC3 = 3.6864 MHz
OSC3 oscillation frequency / Programmable timer settings
Since the underflow signal only is used as the clock source, the
CDR1x/7x register value does not affect the transfer rates.