D12320VF25IV Datasheet, PDF (687/1304 Pages) Renesas Technology Corp – Old Company Name in Catalogs and Other Documents

Section 14 Serial Communication Interface (SCI)
Initialization
[1]
Start of transmission/reception
Read TDRE flag in SSR
[2]
No
TDRE = 1?
Yes
Write transmit data to TDR and
clear TDRE flag in SSR to 0
[1] SCI initialization:
The TxD pin is designated as the
transmit data output pin, and the
RxD pin is designated as the
receive data input pin, enabling
simultaneous transmit and receive
operations.
[2] SCI status check and transmit data
write:
Read SSR and check that the
TDRE flag is set to 1, then write
transmit data to TDR and clear the
TDRE flag to 0.
Transition of the TDRE flag from 0 to
1 can also be identified by a TXI
interrupt.
Read ORER flag in SSR
ORER = 1?
Yes
[3]
[3] Receive error handling:
If a receive error occurs, read the
ORER flag in SSR, and after
performing the appropriate error
handling, clear the ORER flag to 0.
Transmission/reception cannot be
resumed if the ORER flag is set to 1.
No
Error handling
[4] SCI status check and receive data
read:
Read SSR and check that the
Read RDRF flag in SSR
[4]
RDRF flag is set to 1, then read the
receive data in RDR and clear the
RDRF flag to 0. Transition of the
No
RDRF = 1?
RDRF flag from 0 to 1 can also be
identified by an RXI interrupt.
[5]
Yes
Read receive data in RDR, and
clear RDRF flag in SSR to 0
No
All data received?
[5]
Yes
Clear TE and RE bits in SCR to 0
<End>
Notes: When switching from transmit or receive operation to simultaneous
transmit and receive operations, first clear the TE and RE bits to 0,
then set both these bits to 1 simultaneously.
* The DMAC is not supported in the H8S/2321.
Serial transmission/reception
continuation procedure:
To continue serial transmission/
reception, before the MSB (bit 7) of
the current frame is received, finish
reading the RDRF flag, reading
RDR, and clearing the RDRF flag to
0. Also, before the MSB (bit 7) of
the current frame is transmitted,
read 1 from the TDRE flag to
confirm that writing is possible.
Then write data to TDR and clear
the TDRE flag to 0.
Checking and clearing of the TDRE
flag is automatic when the DMAC*
or DTC is activated by a transmit-
data-empty interrupt (TXI) request
and data is written to TDR. Also, the
RDRF flag is cleared automatically
when the DMAC* or DTC is
activated by a receive-data-full
interrupt (RXI) request and the RDR
value is read.
Figure 14.20 Sample Flowchart of Simultaneous Serial Transmit and Receive Operations
Rev.6.00 Sep. 27, 2007 Page 655 of 1268
REJ09B0220-0600