SH7261 Datasheet, PDF (742/1348 Pages) Renesas Technology Corp – 32-Bit RISC Microcomputer SuperHTM RISC engine Family / SH7260 Series

Section 16 Serial Communication Interface with FIFO (SCIF)
(2) Clock
An internal clock generated by the on-chip baud rate generator or an external clock input from the
SCK pin can be selected as the SCIF transmit/receive clock. The clock source is selected by the
C/A bit in the serial mode register (SCSMR) and bits CKE1 and CKE0 in the serial control
register (SCSCR). For clock source selection, refer to table 16.10.
When an external clock is input at the SCK pin, it must have a frequency equal to 16 times the
desired bit rate.
When the SCIF operates on an internal clock, it can output a clock signal on the SCK pin. The
frequency of this output clock is 16 times the desired bit rate.
(3) Transmitting and Receiving Data
• SCIF Initialization (Asynchronous Mode)
Before transmitting or receiving, clear the TE and RE bits to 0 in the serial control register
(SCSCR), then initialize the SCIF as follows.
When changing the operation mode or the communication format, always clear the TE and RE bits
to 0 before following the procedure given below. Clearing TE to 0 initializes the transmit shift
register (SCTSR). Clearing TE and RE to 0, however, does not initialize the serial status register
(SCFSR), transmit FIFO data register (SCFTDR), or receive FIFO data register (SCFRDR), which
retain their previous contents. Clear TE to 0 after all transmit data has been transmitted and the
TEND flag in the SCFSR is set. The TE bit can be cleared to 0 during transmission, but the
transmit data goes to the Mark state after the bit is cleared to 0. Set the TFRST bit in SCFCR to 1
and reset SCFTDR before TE is set again to start transmission.
When an external clock is used, the clock should not be stopped during initialization or subsequent
operation. SCIF operation becomes unreliable if the clock is stopped.
Rev. 2.00 Sep. 07, 2007 Page 710 of 1312
REJ09B0320-0200