Sci Operations During Power-Down State - Renesas H8SX/1650 Hardware Manual

13.9.7

SCI Operations during Power-Down State

(1)
Transmission
Before specifying the module stop state or making a transition to software standby mode, stop the
transmit operations (TE = TIE = TEIE = 0). TSR, TDR, and SSR are reset. The states of the output
pins in the module stop state or in software standby mode depend on the port settings, and the pins
output a high-level signal after 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 cancellation of the power-down state, 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 13.34 shows a sample flowchart for transition to software standby mode during
transmission. Figures 13.35 and 13.36 show the port pin states during transition to software
standby mode.
Before specifying the module stop state or making a transition to software standby mode from the
transmission mode using DTC transfer, stop all transmit operations (TE = TIE = TEIE = 0).
Setting the TE and TIE bits to 1 after cancellation sets the TXI flag to start transmission using the
DTC.
(2)
Reception
Before specifying the module stop state or making a transition to 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 cancellation of the power-down state, set the RE
bit to 1, and then start reception. To receive data in a different reception mode, initialize the SCI
first.
Figure 13.37 shows a sample flowchart for transition to software standby mode during reception.
Section 13 Serial Communication Interface (SCI)
Rev.2.00 Jun. 28, 2007 Page 521 of 666
REJ09B0311-0200