Restrictions On Using Dtc; Notes On Starting Transfer; Sci Operations During Low Power Consumption State - Renesas RX100 Series User Manual

RX13T Group
23.13.7

Restrictions on Using DTC

When using the 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.
23.13.8

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 14, 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.
23.13.9

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.
Figure 23.76 shows a sample flowchart for transition to software standby mode during transmission. Figure 23.77 and
Figure 23.78 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 transfer, stop the transmit operations (TE = 0). To start transmission after cancellation using the DTC, set the TE
and TIE bits 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
(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.
Figure 23.79 shows a sample flowchart for transition to software standby mode during reception.
R01UH0822EJ0100 Rev.1.00
Jul 31, 2019
23. Serial Communications Interface (SCIg, SCIh)
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