Datasheet

Section 17 Serial Communication Interface 3 (SCI3)
Rev. 1.50 Sep. 18, 2007 Page 374 of 584
REJ09B0240-0150
17.3.4 Transmit Data Register (TDR)
TDR is an 8-bit register that stores data for transmission. When the SCI3 detects that TSR is
empty, it transfers the transmit data written in TDR to TSR and starts transmission. The double-
buffered structure of TDR and TSR enables continuous serial transmission. If the next transmit
data has already been written to TDR during transmission of one-frame data, the SCI3 transfers
the written data to TSR to continue transmission. To achieve reliable serial transmission, write
transmit data to TDR only once after confirming that the TDRE bit in SSR is set to 1. TDR is
initialized to H'FF.
17.3.5 Serial Mode Register (SMR)
SMR is used to set the SCI3's serial transfer format and select the baud rate generator clock
source.
Bit Bit Name
Initial
Value R/W Description
7 COM 0 R/W Communication Mode
0: Asynchronous mode
1: Clock synchronous mode
6 CHR 0 R/W Character Length (enabled only in asynchronous mode)
0: Selects 8 bits as the data length.
1: Selects 7 bits as the data length.
5 PE 0 R/W Parity Enable (enabled only in asynchronous mode)
When this bit is set to 1, the parity bit is added to transmit data
before transmission, and the parity bit is checked in reception.
4 PM 0 R/W Parity Mode (enabled only when the PE bit is 1 in
asynchronous mode)
0: Selects even parity.
1: Selects odd parity.
3 STOP 0 R/W Stop Bit Length (enabled only in asynchronous mode)
Selects the stop bit length in transmission.
0: 1 stop bit
1: 2 stop bits
For reception, only the first stop bit is checked, regardless of
the value in the bit. If the second stop bit is 0, it is treated as
the start bit of the next transmit character.