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Rev. 1.00, 05/04, page 273 of 544
12.8.6 SCI Operations during Mode Transitions
Transmission: Before making a transition to module stop, software standby, or sub-sleep mode,
stop all transmit operations (TE = TIE = TEIE = 0). TSR, TDR, and SSR are reset. The states of
the output pins during each mode depend on the port settings, and the pins output a high-level
signal after mode cancellation. If a 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 TE 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 12.21 shows a sample flowchart for mode transition during transmission. Figures 12.22
and 12.23 show the pin states during transmission.
Reception: Before making a transition to module stop, software standby, watch, sub-active, or
sub-sleep mode, stop reception (RE = 0). RSR, RDR, and SSR are reset. If a 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 RE to 1, and then start
reception. To receive data in a different reception mode, initialize the SCI first.
Figure 12.24 shows a sample flowchart for mode transition during reception.