RX610 Group
20. Serial Communications Interface (SCI)
R01UH0032EJ0120 Rev.1.20
Page 675 of 1006
Feb 20, 2013
20.7.6
Restrictions on Clock Synchronous Transmission
When the external clock source is used as a synchronization clock, update TDR by the DMAC or DTC and wait for at
least five clock cycles before allowing the transmit clock to be input. If the transmit clock is input within four clock
cycles after TDR is updated, the SCI may malfunction.
20.7.7
Restrictions on Using DTC or DMAC
When using the DMAC or DTC to read RDR, be sure to set the receive end interrupt (RXI) as the activation source of the
relevant SCI.
20.7.8
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
(TIE = TE = TEIE = 0 in SCR). 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 output pins are held high 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,
and write data to TDR sequentially to start data transmission. To transmit data with a different transmission mode,
initialize the SCI first.
Figure 20.32 shows a sample flowchart for transition to software standby mode during transmission. Figures 20.33 and
20.34 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 the transmit operations (TE = 0). To start transmission after cancellation using the DTC, set the
TE bit to 1. The TXI interrupt flag is set to 1 and transmission starts 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 in SCR). 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 20.35 shows a sample flowchart for mode transition during reception.