External Clock; Internal Clock - Toshiba TLCS-870/C Series Manual

12. Synchronous Serial Interface (SIO)
12.3 Serial clock

12.3.1.1 Internal clock

SCK pin goes high when transfer starts.
cannot keep up with the serial clock rate, there is a wait function that automatically stops the serial clock
and holds the next shift operation until the read/write processing is completed.
Table 12-1 Serial Clock Rate
SCK
000
001
010
011
100
101
110
111
SCK
pin (output)
SO
pin (output)
Written transmit
data

12.3.1.2 External clock

port should be set to "1". To ensure shifting, a pulse width of at least 4 machine cycles is required. This
pulse is needed for the shift operation to execute certainly. Actually, there is necessary processing time for
interrupting, writing, and reading. The minimum pulse is determined by setting the mode and the pro-
gram. Therfore, maximum transfer frequency will be 488.3K bit/sec (at fc=16MHz).
SCK
pin (Output)
Any of six frequencies can be selected. The serial clock is output to the outside on the SCK pin. The
When data writing (in the transmit mode) or reading (in the receive mode or the transmit/receive mode)
NORMAL1/2, IDLE1/2 mode
DV7CK = 0
Clock Baud Rate
13
1.91 Kbps
fc/2
8
61.04 Kbps
fc/2
7
122.07 Kbps
fc/2
6
244.14 Kbps
fc/2
5
488.28 Kbps
fc/2
4
976.56 Kbps
fc/2
- -
External External
Note: 1 Kbit = 1024 bit (fc = 16 MHz, fs = 32.768 kHz)
a a
0 1
a
Figure 12-3 Automatic Wait Function (at 4-bit transmit mode)
An external clock connected to the
t t
SCKL SCKH
Figure 12-4 External clock pulse width
DV7CK = 1
Clock
5
fs/2
8
fc/2
7
fc/2
6
fc/2
5
fc/2
4
fc/2
-
External
Automatically
wait function
a a
2 3
b
pin is used as the serial clock. In this case, output latch of this
SCK
tcyc = 4/fc (In the NORMAL1/2, IDLE1/2 modes)
4/fs (In the SLOW1/2, SLEEP1/2 modes)
t , t
SCKL SCKH
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TMP86PM29BUG
SLOW1/2,
SLEEP1/2 mode
Baud Rate Clock
5
1024 bps
fs/2
61.04 Kbps -
122.07 Kbps -
244.14 Kbps -
488.28 Kbps -
976.56 Kbps -
- -
External External
b b b b c
0 1 2 3 0
c
> 4tcyc
Baud Rate
1024 bps
-
-
-
-
-
-
External
c
1