Datasheet

Section 15 Serial Communication Interface (SCI)
Rev. 6.00 Mar. 18, 2010 Page 609 of 982
REJ09B0054-0600
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 final bitof the
current frame is received, finish
reading the RDRF flag, reading RDR,
and clearing the RDRF flag to 0.
Also, before the final bit 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 DTC
*
2
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
*
1
or the DTC
*
2
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 by one instruction simultaneously.
1. Supprted only by the H8S/2239 Group.
2. The case, in which the DTC automatically clears the TDRE flag or RDRF flag, occurs only when DISEL
in the corresponding DTC transfer is 0 with the transfer counter not being 0. Therefore, the
corresponding flag should be cleared by CPU when DISEL in the corresponding DTC transfer is 1, or
when DISEL is 0 with the transfer counter being 0.
Figure 15.23 Sample Flowchart of Simultaneous Serial Transmit and Receive Operations