HD64F2357F20V Datasheet, PDF (531/1049 Pages) Renesas Technology Corp – Hardware Manual Renesas 16-Bit Single-chip Microcomputer H8S Family / H8S/2300 Series

In serial transmission, the SCI operates as described below.
[1] The SCI monitors the TDRE flag in SSR, and if is 0, recognizes that data has been written to TDR, and transfers the
data from TDR to TSR.
[2] After transferring data from TDR to TSR, the SCI sets the TDRE flag to 1 and starts transmission.
If the TIE bit is set to 1 at this time, a transmit data empty interrupt (TXI) is generated.
The serial transmit data is sent from the TxD pin in the following order.
[a] Start bit:
One 0-bit is output.
[b] Transmit data:
8-bit or 7-bit data is output in LSB-first order.
[c] Multiprocessor bit
One multiprocessor bit (MPBT value) is output.
[d] Stop bit(s):
One or two 1-bits (stop bits) are output.
[e] Mark state:
1 is output continuously until the start bit that starts the next transmission is sent.
[3] The SCI checks the TDRE flag at the timing for sending the stop bit.
If the TDRE flag is cleared to 0, data is transferred from TDR to TSR, the stop bit is sent, and then serial transmission
of the next frame is started.
If the TDRE flag is set to 1, the TEND flag in SSR is set to 1, the stop bit is sent, and then the mark state is entered in
which 1 is output continuously. If the TEIE bit in SCR is set to 1 at this time, a transmission end interrupt (TEI)
request is generated.
Figure 14-11 shows an example of SCI operation for transmission using the multiprocessor format.
Start
1 bit
0 D0 D1
Data
Multi-
proce-
ssor Stop
bit bit
Start
bit
Data
Multi-
proces- Stop
sor bit bit 1
D7 0/1 1 0 D0 D1
D7 0/1
1 ^{Idle state}
(mark state)
TDRE
TEND
TXI interrupt
request generated
Data written to TDR
and TDRE flag cleared to
0 in TXI interrupt service
routine
TXI interrupt
request generated
1 frame
TEI interrupt
request generated
Figure 14-11 Example of SCI Operation in Transmission
(Example with 8-Bit Data, Multiprocessor Bit, One Stop Bit)
Rev.6.00 Oct.28.2004 page 501 of 1016
REJ09B0138-0600H