R01UH0823EJ0100 Rev.1.00
Page 1034 of 1823
Jul 31, 2019
RX23W Group
33. Serial Communications Interface (SCIg, SCIh)
33.4.1
Multi-Processor Serial Data Transmission
is a sample flowchart of multi-processor data transmission. In the ID transmission cycle, the ID should be
transmitted with the SSR.MPBT bit set to 1. In the data transmission cycle, the data should be transmitted with the
MPBT bit set to 0. The other operations are the same as the operations in asynchronous mode.
Figure 33.19
Example of Multi-Processor Serial Transmission Flowchart
No
End
Yes
Initialization
Start data transmission
Set MPBT bit in SSR
No
Yes
No
Yes
Set the SCR.TIE bit to 0, and
set the SCR.TEIE bit to 1
No
Yes
Set the I/O port functions
Set bits TE, TIE, and TEIE in SCR to 0
TXI interrupt
All data written?
TEI interrupt
Break output
Write transmit data to TDR
[ 3 ]
[ 1 ]
[ 4 ]
[ 2 ]
Note:
The TDR register becomes the TDRH and TDRL
registers when 9-bit data length is selected. Write
data in the order from TDRH to TDRL.
[ 1 ]
SCI initialization:
Set data transmission.
After the TE bit in SCR is set to 1, high is output for a
frame, and transmission is enabled.
[ 2 ]
TXI interrupt request:
When transmit data is transferred from TDR to TSR, a
transmit data empty interrupt (TXI) request is
generated.
Set the MPBT bit in SSR to 0 or 1, and write transmit
data to TDR once in the TXI interrupt handling routine.
[ 3 ]
Serial transmission continuation procedure:
To continue serial transmission, write transmit data to
TDR once using a TXI interrupt request.
Transmit data can also be written to TDR by activating
the DMAC or DTC.
When TEI interrupt requests are in use, set the
SCR.TIE bit to 0 and the SCR.TEIE bit to 1 after the last
of the data to be transmitted are written to the TDR.
[ 4 ]
Break output at the end of serial transmission:
To output a break in serial transmission, set the I/O port
function corresponding to the TXDn pin (corresponding
to output of the low level), and after switching the TXDn
pin to the general I/O port function, set the TE bit in the
SCR to 0.