H8SSLASH2225 datasheet(699/1071 Pages) RENESAS

699 / 1071 page

Section 15 Serial Communication Interface (SCI)

Rev. 5.00 Aug 08, 2006 page 613 of 982

REJ09B0054-0500

M = (0.5 – 1/2

× 372) × 100%

= 49.866%

Internal

basic clock

372 clocks

186 clocks

Receive data

(RxD)

Synchronization

sampling timing

Data sampling

timing

185

371 0

371

185

Start bit

Figure 15.28 Receive Data Sampling Timing in Smart Card Mode

(Using Clock of 372 Times the Transfer Rate)

15.7.5

Initialization

Before transmitting and receiving data, initialize the SCI as described below. Initialization is also

necessary when switching from transmit mode to receive mode, or vice versa.

1. Clear the TE and RE bits in SCR to 0.

2. Clear the error flags ERS, PER, and ORER in SSR to 0.

3. Set the GM, BLK, O/

E, BCP0, BCP1, CKS0, CKS1 bits in SMR. Set the PE bit to 1.

4. Set the SMIF, SDIR, and SINV bits in SCMR.

When the SMIF bit is set to 1, the TxD and RxD pins are both switched from ports to SCI pins,

and are placed in the high-impedance state.

5. Set the value corresponding to the bit rate in BRR.

6. Set the CKE0 and CKE1 bits in SCR. Clear the TIE, RIE, TE, RE, MPIE, and TEIE bits to 0.

If the CKE0 bit is set to 1, the clock is output from the SCK pin.

7. Wait at least one bit interval, then set the TIE, RIE, TE, and RE bits in SCR. Do not set the TE

bit and RE bit at the same time, except for self-diagnosis.

To switch from receive mode to transmit mode, after checking that the SCI has finished reception,

initialize the SCI, and set RE to 0 and TE to 1. Whether SCI has finished reception or not can be

checked with the RDRF, PER, or ORER flags. To switch from transmit mode to receive mode,

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