R01UH0823EJ0100 Rev.1.00
Page 1100 of 1823
Jul 31, 2019
RX23W Group
33. Serial Communications Interface (SCIg, SCIh)
33.14.7
Restrictions on Using DMAC or DTC
When using the DMAC or DTC to read RDR, RDRH, and RDRL, be sure to set the receive data full interrupt (RXI) as
the activation source of the relevant SCI.
33.14.8
Notes on Starting Transfer
At the point where transfer starts when the interrupt status flag (IRn.IR flag) in the interrupt controller is 1, follow the
procedure below to clear interrupt requests before permitting operations (by setting the SCR.TE or SCR.RE bit to 1). For
details on the interrupt status flag, refer to
section 15, Interrupt Controller (ICUb)
Confirm that transfer has stopped (the setting of the SCR.TE or SCR.RE bits is 0).
Set the corresponding interrupt enable bit (SCR.TIE or SCR.RIE) to 0.
Read the corresponding interrupt enable bit (SCR.TIE or SCR.RIE bit) to check that it has become 0.
Set the interrupt status flag (IRn.IR flag) in the interrupt controller to 0.
33.14.9
SCI Operations during Low Power Consumption State
(1) Transmission
When making settings for the module stopped state or in transitions to software standby, stop operations (by setting the
TIE, TE, and TEIE bits in the SCR register to 0) after switching the TXDn pin to the general I/O port pin function.
Setting the TE bit to 0 resets the TSR register and the SSR.TEND flag. Depending on the port settings, output pins may
output the level before a transition to the low power consumption state is made after release from the module stopped
state or software standby mode. When transitions to these states are made during transmission, the data being transmitted
become indeterminate.
To transmit data in the same transmit mode after cancellation of the low power consumption 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 transmit mode,
initialize the SCI first.
shows a sample flowchart for transition to software standby mode during transmission.
and
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 transmit mode using
DTC/DMA transfer, stop the transmit operations (TE = 0). To start transmission after cancellation using the DTC/
DMAC, set the TE and TIE bits to 1. The TXI interrupt flag is set to 1 and transmission starts using the DTC/DMAC.
(2) Reception
Before specifying the module stop state or making a transition to software standby mode, stop the receive operations
(SCR.RE = 0). If transition is made during data reception, the data being received will be invalid.
To receive data in the same receive mode after cancellation of the low power consumption state, set the RE bit to 1, and
then start reception. To receive data in a different receive mode, initialize the SCI first.
shows a sample flowchart for transition to software standby mode during reception.