HD64F3670 Datasheet, PDF (216/323 Pages) Renesas Technology Corp – Hitachi Single-Chip Microcomputer

13.8.3 Receive Error Flags and Transmit Operations (Clocked Synchronous Mode Only)
Transmission cannot be started when a receive error flag (OER, PER, or FER) is set to 1, even if
the TDRE flag is cleared to 0. Be sure to clear the receive error flags to 0 before starting
transmission. Note also that receive error flags cannot be cleared to 0 even if the RE bit is cleared
to 0.
Rev. 2.0, 03/02, page 192 of 298