h8s-2138 Renesas Electronics Corporation., h8s-2138 Datasheet - Page 500

• Manufacturer Part Number: h8s-2138
• Description: Renesas 16-bit Single-chip Microcomputer H8s Family/h8s/2100 Series
• Manufacturer: Renesas Electronics Corporation.

Section 15 Serial Communication Interface (SCI, IrDA)
Rev. 4.00 Jun 06, 2006 page 446 of 1004
REJ09B0301-0400
Figure 15.20 Sample Flowchart of Simultaneous Serial Transmit and Receive Operations
Note: 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.
No
No
No
Clear TE and RE bits in SCR to 0
Read receive data in RDR, and
Write transmit data to TDR and
Start transmission/reception
clear TDRE flag in SSR to 0
clear RDRF flag in SSR to 0
Read ORER flag in SSR
Read TDRE flag in SSR
Read RDRF flag in SSR
All data received?
Initialization
ORER = 1?
TDRE = 1?
RDRF = 1?
<End>
Yes
Yes
Yes
No
Error handling
Yes
[1]
[2]
[4]
[5]
[3]
[1]
[2]
[3]
[4]
[5]
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.
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.
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.
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.
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 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
DTC is activated by a receive-data-
full interrupt (RXI) request and the
RDR value is read.