HD64F3039F18 Datasheet, PDF (389/710 Pages) Renesas Technology Corp – Renesas 16-Bit Single-Chip Microcomputer H8 Family / H8/300H Series

Section 11 Serial Communication Interface
In transmitting serial data, the SCI operates as follows.
• The SCI monitors the TDRE flag in SSR. When the TDRE flag is cleared to 0 the SCI
recognizes that TDR contains new data, and loads this data from TDR into TSR.
• After loading the data from TDR into TSR, the SCI sets the TDRE flag to 1 and starts
transmitting. If the TIE bit is set to 1 in SCR, the SCI requests a transmit-data-empty interrupt
(TXI) at this time.
Serial transmit data is transmitted in the following order from the TxD pin:
 Start bit:
One 0 bit is output.
 Transmit data:
7 or 8 bits are output, LSB first.
 Parity bit or multiprocessor bit: One parity bit (even or odd parity) or one multiprocessor
bit is output. Formats in which neither a parity bit nor
a multiprocessor bit is output can also be selected.
 Stop bit:
One or two 1 bits (stop bits) are output.
 Mark state:
Output of 1 continues until the start bit of the next
transmit data.
• The SCI checks the TDRE flag when it outputs the stop bit. If the TDRE flag is 0, the SCI
loads new data from TDR into TSR, outputs the stop bit, then begins serial transmission of the
next frame. If the TDRE flag is 1, the SCI sets the TEND flag to 1 in SSR, outputs the stop bit,
then continues output of 1 in the mark state. If the TEIE bit is set to 1 in SCR, a transmit-end
interrupt (TEI) is requested at this time.
Figure 11.6 shows an example of SCI transmit operation in asynchronous mode.
Start
1
bit
Data
Parity Stop Start
bit bit bit
Parity Stop
Data
bit bit
1
0 D0 D1
D7 0/1 1 0 D0 D1
D7 0/1 1
Idle (mark)
state
TDRE
TEND
TXI
TXI interrupt handler
interrupt writes data in TDR and
request clears TDRE flag to 0
1 frame
TXI
interrupt
request
TEI interrupt request
Figure 11.6 Example of SCI Transmit Operation in Asynchronous Mode
(8-Bit Data with Parity and 1 Stop Bit)
Rev.3.00 Mar. 26, 2007 Page 365 of 682
REJ09B0353-0300