H8SSLASH2214 datasheet(584/936 Pages) RENESAS

584 / 936 page

Section 12 Serial Communication Interface (SCI)

Rev.4.00 Sep. 18, 2008 Page 524 of 872

REJ09B0189-0400

LSB

Serial data

SCK

Note: When operating on an external clock, set t > 4 clocks.

TDRE

Figure 12.27 Example of Clocked Synchronous Transmission by DTC

(9) Operation in Case of Mode Transition

(a) Transmission

Operation should be stopped (by clearing TE, TIE, and TEIE to 0) before making a module stop

mode, software standby mode, or subsleep mode transition. TSR, TDR, and SSR are reset. The

output pin states in module stop mode, software standby mode, or subsleep mode depend on the

port settings, and becomes high-level output after the relevant mode is cleared. If a transition is

made during transmission, the data being transmitted will be undefined. When transmitting

without changing the transmit mode after the relevant mode is cleared, transmission can be started

by setting TE to 1 again, and performing the following sequence: SSR read -> TDR write ->

TDRE clearance. To transmit with a different transmit mode after clearing the relevant mode, the

procedure must be started again from initialization. Figure 12.28 shows a sample flowchart for

mode transition during transmission. Port pin states are shown in figures 12.29 and 12.30.

Operation should also be stopped (by clearing TE, TIE, and TEIE to 0) before making a transition

from transmission by DTC transfer to module stop mode, software standby mode, or subsleep

mode transition. To perform transmission with the DTC after the relevant mode is cleared, setting

TE and TIE to 1 will set the TXI flag and start DTC transmission.

(b) Reception

Receive operation should be stopped (by clearing RE to 0) before making a module stop mode,

software standby mode, watch mode, subactive mode, or subsleep mode transition. RSR, RDR,

and SSR are reset. If a transition is made without stopping operation, the data being received will

be invalid.

To continue receiving without changing the reception mode after the relevant mode is cleared, set

RE to 1 before starting reception. To receive with a different receive mode, the procedure must be

started again from initialization.

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