H8S78 Datasheet, PDF (763/1208 Pages) Renesas Technology Corp – Renesas 16-Bit Single-Chip Microcomputer H8S Family/H8S/2300 Series

Section 15 Serial Communication Interface (SCI, IrDA)
already been written to TDR during serial transmission, the SCI transfers the written data to TSR
to continue transmission. Although TDR can be read or written to by the CPU at all times, to
achieve reliable serial transmission, write transmit data to TDR for only once after confirming that
the TDRE bit in SSR is set to 1.
15.3.4 Transmit Shift Register (TSR)
TSR is a shift register that transmits serial data. To perform serial data transmission, the SCI first
transfers transmit data from TDR to TSR, then sends the data to the TxD pin starting. TSR cannot
be directly accessed by the CPU.
15.3.5 Serial Mode Register (SMR)
SMR is used to set the SCI’s serial transfer format and select the on-chip baud rate generator clock
source.
Some bit functions of SMR differ in normal serial communication interface mode and Smart Card
interface mode.
Normal Serial Communication Interface Mode (When SMIF in SCMR is 0)
Bit Bit Name Initial Value R/W
7
C/A
0
R/W
6
CHR
0
R/W
Description
Communication Mode
0: Asynchronous mode
1: Clocked synchronous mode
Character Length (enabled only in asynchronous
mode)
0: Selects 8 bits as the data length.
1: Selects 7 bits as the data length. LSB-first is
fixed and the MSB (bit 7) of TDR is not
transmitted in transmission.
In clocked synchronous mode, a fixed data length
of 8 bits is used.
Rev.7.00 Mar. 18, 2009 page 695 of 1136
REJ09B0109-0700