TMPM330 - Keil

10.7.1 Serial Clock
SCK pin output
SO pin output
Write the
transmit data
Clock source
Under development
TMPM330 (rev 0.4) 10-31
TMPM330
Internal or external clocks can be selected by programming SBIxCR1 .
Internal clocks
In the internal clock mode, one of the seven frequencies can be selected as a serial
clock, which is output to the outside through the SCK pin. At the beginning of a
transfer, the SCK pin output becomes the “H” level.
If the program cannot keep up with this serial clock rate in writing the transmit data or
reading the received data, the SBI automatically enters a wait period. During this
period, the serial clock is stopped automatically and the next shift operation is
suspended until the processing is completed.
External clock ( = “111”)
Automatic wait
1 2 3 7 8 1 2 6 7 8 1 2 3
a0 a1 a2a5 a6 a7 b0 b1 b4 b5 b6 b7 c0 c1 c2
a b c
Fig. 10-24 Automatic Wait
The SBI uses an external clock supplied from the outside to the SCK pin as a serial
clock. For proper shift operations, the serial clock at the “H” and “L” levels must have
the pulse widths as shown below.
SCK pin
tSCKL
tSCKH
tSCKL, tSCKH > 8/fsys
Fig. 10-25 Maximum Transfer Frequency of External Clock Input
Serial Bus Interface (SBI)