Hardware manual

Rev. 3.0, 09/98, page 212 of 361
• Receiving Serial Data: Follow the procedure below for receiving serial data.
Start receiving
Read RDRF bit in SSR
RDRF = "1"?
Read receive data from
RDR, and clear RDRF bit
to "0" in SSR
PER RER
ORER= "1"?
Clear RE to "0" in SCR
Finished
receiving?
End
Error handling
Start error handling
FER = "1"?
Clear error flags
to "0" in SCR
Return
Break?
Clear RE to "0"
in SCR
End
1
2
No
Yes
Yes
No
No
Yes
4
1.
2.
3.
4.
SCI initialization: the receive data function of the RxD pin is
selected automatically.
SCI status check and receive data read: read the serial status
register (SSR), check that RDRF is set to "1," then read receive
data from the receive data register (RDR) and clear RDRF to "0."
Transition of the RDRF bit from "0" to "1" can be reported by an
RXI interrupt.
To continue receiving serial data: read RDR and clear RDRF to
"0" before the stop bit of the current frame is received.
Receive error handling and break detection: if a receive error
occurs, read the ORER, PER, and FER bits in SSR to identify
the error. After executing the necessary error handling, clear
ORER, PER, and FER all to "0." Transmitting and receiving
cannot resume if ORER, PER, or FER remains set to "1."
When a framing error occurs, the RxD pin can be read to detect
the break state.
Yes
No
Yes
No
Read ORER, PER, and
FER in SSR
3
Initialize
^^
Figure 10.7 Sample Flowchart for Receiving Serial Data