Sci Operations During Mode Transitions - Renesas H8SX/1520 Series Hardware Manual

32-bit cisc microcomputer

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Section 12 Serial Communication Interface (SCI)

SCI Operations during Mode Transitions

Transmission

Before making the transition to module stop mode or software standby mode, stop the transmit

operations (TE = TIE = TEIE = 0). TSR, TDR, and SSR are reset. The states of the output pins

during module stop mode or software standby mode depend on the port settings, and the pins

output a high-level signal after mode cancellation. If the transition is made during data

transmission, the data being transmitted will be undefined.

To transmit data in the same transmission mode after mode cancellation, set the TE bit to 1, read

SSR, write to TDR, clear TDRE in this order, and then start transmission. To transmit data in a

different transmission mode, initialize the SCI first.

Figure 12.34 shows a sample flowchart for mode transition during transmission. Figures 12.35 and

12.36 show the port pin states during mode transition.

Before making the transition to module stop mode or software standby mode, stop the receive

operations (RE = 0). RSR, RDR, and SSR are reset. If transition is made during data reception, the

data being received will be invalid.

To receive data in the same reception mode after mode cancellation, set the RE bit to 1, and then

start reception. To receive data in a different reception mode, initialize the SCI first.

Rev. 3.00 Mar. 14, 2006 Page 444 of 804

REJ09B0104-0300

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