Datasheet

Section 15 Serial Communication Interface (SCI)
Rev. 3.00 Sep. 28, 2009 Page 462 of 910
REJ09B0350-0300
15.9.6 SCI Operations during Mode Transitions
(1) Transmission
Before making the transition to module stop or software standby, 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 is cancelled and
then the TE is set to 1 again. 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 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 15.33 shows a sample flowchart for mode transition during transmission. Figures 15.34 and
15.35 show the pin states during transmission.
Start transmission
Transmission
[1]
No
No
No
Yes
Yes
Yes
Read TEND flag in SSR
Make transition to
software standby mode etc.
Cancel software standby mode etc.
TE = 0
Initialization TE = 1
[2]
[3]
All data transmitted?
Change operating mode?
TEND = 1
[1] Data being transmitted is lost halfway.
Data can be normally transmitted from
the CPU by setting TE to 1, reading
SSR, writing to TDR, and clearing
TDRE to 0 after mode cancellation.
[2] Also clear TIE and TEIE to 0 when
they are 1.
[3] Module stop mode and watch mode
are included.
Figure 15.33 Sample Flowchart for Mode Transition during Transmission