Datasheet

Table Of Contents
Section 13 Serial Communication Interface
Page 446 of 846 REJ09B0140-0900 Rev. 9.00
Sep 16, 2010
H8S/2215 Group
Yes
<End>
[1]
No
Initialization
Start transmission/reception
[5]
Error processing
[3]
Read receive data in RDR, and
clear RDRF flag in SSR to 0
No
Yes
ORER = 1
All data received?
[2]
Read TDRE flag in SSR
No
Yes
TDRE = 1
Write transmit data to TDR and
clear TDRE flag in SSR to 0
No
Yes
RDRF = 1
Read ORER flag in SSR
[4]
Read RDRF flag in SSR
Clear TE and RE bits in SCR 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.
[3] Receive error processing:
If a receive error occurs, read the ORER
flag in SSR, and after performing the
appropriate error processing, clear the
ORER flag to 0. Transmission/reception
cannot be resumed if the ORER flag is
set to 1.
[4] SCI status check and receive data read:
Read SSR and check that the RDRF flag
is set to 1, then read the receive data in
RDR and clear the RDRF flag to 0.
Transition of the RDRF flag from 0 to 1
can also be identified by an RXI
interrupt.
[5] 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 the
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
the DTC* is activated by a receive data
full interrupt (RXI) request and the RDR
value is read.
Notes: When switching from transmit or receive operation to simultaneous
transmit and receive operations, first clear the TE bit and RE bit to 0,
then set both these bits to 1 simultaneously.
* The TDRE and RDRF flags are automatically cleared by the DTC
when the DTC's DISEL bit is cleared to 0 and the transfer counter
value is not 0. Consequently, it is necessary to use the CPU to
clear the TDRE and RDRF flags if DISEL is set to 1 or if the
transfer counter value is 0.
Figure 13.24 Sample Flowchart of Simultaneous Serial Transmit and Receive Operations