HD64F2149YV datasheet(459/1075 Pages) RENESAS

459 / 1075 page

Section 15 Serial Communication Interface (SCI, IrDA)

Rev. 3.00 Jan 18, 2006 page 431 of 1044

REJ09B0280-0300

15.2.3

Transmit Shift Register (TSR)

—

Bit

Read/Write

TSR is a register used to transmit 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 with the LSB (bit 0).

When transmission of one byte is completed, the next transmit data is transferred from TDR to

TSR, and transmission started, automatically. However, data transfer from TDR to TSR is not

performed if the TDRE bit in SSR is set to 1.

TSR cannot be directly read or written to by the CPU.

15.2.4

Transmit Data Register (TDR)

R/W

Bit

Initial value

Read/Write

TDR is an 8-bit register that stores data for serial transmission.

When the SCI detects that TSR is empty, it transfers the transmit data written in TDR to TSR and

starts serial transmission. Continuous serial transmission can be carried out by writing the next

transmit data to TDR during serial transmission of the data in TSR.

TDR can be read or written to by the CPU at all times.

TDR is initialized to H'FF by a reset, and in standby mode, watch mode, subactive mode, subsleep

mode, and module stop mode.

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