Transmit Shift Register (Sctsr1); Transmit Data Register (Sctdr1) - Hitachi SH7751 Hardware Manual

15.2.3

Transmit Shift Register (SCTSR1)

Bit: 7
R/W: —
SCTSR1 is the register used to transmit serial data.
To perform serial data transmission, the SCI first transfers transmit data from SCTDR1 to
SCTSR1, then sends the data to the TxD pin starting with the LSB (bit 0).
When transmission of one byte is completed, the next transmit data is transferred from SCTDR1
to SCTSR1, and transmission started, automatically. However, data transfer from SCTDR1 to
SCTSR1 is not performed if the TDRE flag in the serial status register (SCSSR1) is set to 1.
SCTSR1 cannot be directly read or written to by the CPU.
15.2.4

Transmit Data Register (SCTDR1)

Bit: 7
Initial value: 1
R/W: R/W
SCTDR1 is an 8-bit register that stores data for serial transmission.
When the SCI detects that SCTSR1 is empty, it transfers the transmit data written in SCTDR1 to
SCTSR1 and starts serial transmission. Continuous serial transmission can be carried out by
writing the next transmit data to SCTDR1 during serial transmission of the data in SCTSR1.
SCTDR1 can be read or written to by the CPU at all times.
SCTDR1 is initialized to H'FF by a power-on reset or manual reset, in standby mode, and in the
module standby state.
Rev. 3.0, 04/02, page 574 of 1064
6 5
— —
6 5
1 1
R/W R/W
4 3
— —
4 3
1 1
R/W R/W R/W
2 1
— — —
2 1
1 1
R/W R/W
0
0
1