HD64F2149YV datasheet(504/1075 Pages) RENESAS

504 / 1075 page

Section 15 Serial Communication Interface (SCI, IrDA)

Rev. 3.00 Jan 18, 2006 page 476 of 1044

REJ09B0280-0300

Clock

Either an internal clock generated by the built-in baud rate generator or an external serial clock

input at the SCK pin can be selected, according to the setting of the C/

A bit in SMR and the CKE1

and CKE0 bits in SCR. For details on SCI clock source selection, see table 15.9.

When the SCI is operated on an internal clock, the serial clock is output from the SCK pin.

Eight serial clock pulses are output in the transfer of one character, and when no transfer is

performed the clock is fixed high. When only receive operations are performed, however, the

serial clock is output until an overrun error occurs or the RE bit is cleared to 0. To perform receive

operations in units of one character, select an external clock as the clock source.

Data Transfer Operations

SCI Initialization (Synchronous Mode): Before transmitting and receiving data, first clear the

TE and RE bits in SCR to 0, then initialize the SCI as described below.

When the operating mode, transfer format, etc., is changed, the TE and RE bits must be cleared to

0 before making the change using the following procedure. When the TE bit is cleared to 0, the

TDRE flag is set to 1 and TSR is initialized. Note that clearing the RE bit to 0 does not change the

settings of the RDRF, PER, FER, and ORER flags, or the contents of RDR.

Figure 15.15 shows a sample SCI initialization flowchart.

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