Sci Operations During Mode Transitions - Renesas H8S/2100 Series Hardware Manual

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.
All data transmitted?
Read TEND flag in SSR
Make transition to
software standby mode etc.
Cancel software standby mode etc.
Change operating mode?
Figure 15.33 Sample Flowchart for Mode Transition during Transmission
Transmission
No
Yes
No
TEND = 1
Yes
TE = 0
[2]
No
Yes
Initialization
Start transmission
Section 15 Serial Communication Interface (SCI)
[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.
[3]
TE = 1
Rev. 1.00 Apr. 28, 2008 Page 463 of 994
REJ09B0452-0100