HD64F2145 Datasheet, PDF (404/829 Pages) Renesas Technology Corp – Hitachi 16-Bit Single-Chip Microcomputer

15.4.6 Serial Data Reception (Asynchronous Mode)
Figure 15.8 shows an example of the operation for reception in asynchronous mode. In serial
reception, the SCI operates as described below.
1. The SCI monitors the communication line, and if a start bit is detected, performs internal
synchronization, receives receive data in RSR, and checks the parity bit and stop bit.
2. If an overrun error (when reception of the next data is completed while the RDRF flag in SSR
is still set to 1) occurs, the ORER bit in SSR is set to 1. If the RIE bit in SCR is set to 1 at this
time, an ERI interrupt request is generated. Receive data is not transferred to RDR. The RDRF
flag remains to be set to 1.
3. If a parity error is detected, the PER bit in SSR is set to 1 and receive data is transferred to
RDR. If the RIE bit in SCR is set to 1 at this time, an ERI interrupt request is generated.
4. If a framing error (when the stop bit is 0) is detected, the FER bit in SSR is set to 1 and receive
data is transferred to RDR. If the RIE bit in SCR is set to 1 at this time, an ERI interrupt
request is generated.
5. If reception finishes successfully, the RDRF bit in SSR is set to 1, and receive data is
transferred to RDR. If the RIE bit in SCR is set to 1 at this time, an RXI interrupt request is
generated. Because the RXI interrupt routine reads the receive data transferred to RDR before
reception of the next receive data has finished, continuous reception can be enabled.
Start
1 bit
Data
Parity Stop Start
bit bit bit
Data
Parity Stop
bit bit
1
0 D0 D1
D7 0/1 1 0 D0 D1
D7 0/1
0
Idle state
(mark state)
RDRF
FER
RXI interrupt
request
generated
RDR data read and RDRF
flag cleared to 0 in RXI
interrupt handling routine
1 frame
ERI interrupt request
generated by framing
error
Figure 15.8 Example of SCI Receive Operation in Asynchronous Mode (Example with 8-Bit
Data, Parity, One Stop Bit)
Rev. 2.0, 08/02, page 364 of 788