4524_M Datasheet, PDF (229/310 Pages) Renesas Technology Corp – 4-BIT CISC SINGLE-CHIP MICROCOMPUTER 720 FAMILY / 4500 SERIES

4524 Group
APPLICATION
2.5 Serial I/O
2.5.5 Notes on use
(1) Note when an external clock is used as a synchronous clock:
• An external clock is selected as the synchronous clock, the clock is not controlled internally.
• Serial transmit/receive is continued as long as an external clock is input. If an external clock is input
9 times or more and serial transmit/receive is continued, the receive data is transferred directly as
transmit data, so that be sure to control the clock externally.
Note also that the SIOF flag is set to “1” when a clock is counted 8 times.
• Be sure to set the initial input level on the external clock pin to “H” level.
• Refer to section “3.1 Electrical characteristics” when using serial I/O with an external clock.
Rev.2.00 Aug, 06 2004
REJ09B0107-0200Z
2-65