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CHAPTER 9 8-BIT SERIAL I/O
9.10 Program Example for 8-bit Serial I/O
This section gives program example for 8-bit serial I/O.
■ Program example for serial output
●
Processing description
• Outputs 8-bit serial data (55
H
) from the SO pin of serial I/O, then generates an interrupt when transfer is
completed.
• The interrupt processing routine resets the transfer data and continues output.
• Operates as an internal shift clock and outputs the shift clock from the SCK pin.
• With a main clock oscillation frequency F
CH
of 5 MHz, the highest speed clock selected by the speed-
shift function (1 instruction cycle = 4/F
CH
), and a 32 t
inst
shift clock, the data transfer rate will be as
follows.
Transfer speed = 5 MHz/4/32 = 39 kbps
Interrupt cycle = 8 x 32 x 4/5 MHz = 204.8 µs