SH7125_08 Datasheet, PDF (485/774 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperH™ RISC engine Family

Section 12 Serial Communication Interface (SCI)
12.4.5 Multiprocessor Serial Data Transmission
Figure 12.16 shows a sample flowchart for multiprocessor serial data transmission. For an ID
transmission cycle, set the MPBT bit in SCSSR to 1 before transmission. For a data transmission
cycle, clear the MPBT bit in SCSSR to 0 before transmission. Note that the MPBT bit must be
held 1 until when an ID is transmitted. All other SCI operations are the same as those in
asynchronous mode.
Initialization
[1]
Start transmission
Read TDRE flag in SCSSR
[2]
No
TDRE = 1?
Yes
Write transmit data to SCTDR and
set MPBT bit in SCSSR
Clear TDRE flag to 0
All data transmitted?
Yes
Read TEND flag in SCSSR
TEND = 1?
Yes
Break output?
Yes
Clear DR to 0
No
[3]
No
No
[4]
Clear TE bit in SCSCR to 0;
select the TXD pin
as an output port with the PFC
[1] SCI initialization:
Set the TXD pin using the PFC.
After the TE bit is set to 1, 1 is output
for one frame, and transmission is
enabled. However, data is not
transmitted.
[2] SCI status check and transmit data
write:
Read SCSSR and check that the
TDRE flag is set to 1, then write
transmit data to SCTDR. Set the
MPBT bit in SCSSR to 0 or 1. Finally,
clear the TDRE flag to 0.
After initializing the SCI, when an ID
is written to SCTDR register so as to
transmit the ID, data is immediately
transferred, and then the TDER flag is
set to 1. The MPBT bit must be held 1
because the ID is not transmitted from
the TXD pin at this time. When the
TDRE flag is set to 1 after data
following the ID is written to SCTDR,
clear the MPBT bit to 0.
[3] Serial transmission continuation
procedure:
To continue serial transmission, be
sure to read 1 from the TDRE flag to
confirm that writing is possible, then
write data to SCTDR, and then clear
the TDRE flag to 0.
[4] Break output at the end of serial
transmission:
To output a break in serial
transmission, first clear the port data
register (DR) to 0, then clear the TE
bit to 0 in SCSCR and use the PFC to
select the TXD pin as an output port.
<End>
Figure 12.16 Sample Multiprocessor Serial Transmission Flowchart
Rev. 4.00 Jul. 25, 2008 Page 465 of 750
REJ09B0243-0400