How-To Guide

Table Of Contents
R01UH0823EJ0110 Rev.1.10 Page 980 of 1852
Nov 30, 2020
RX23W Group 33. Serial Communications Interface (SCIg, SCIh)
33.2.5 Transmit Data Register H, L, HL (TDRH, TDRL, TDRHL)
Transmit Data Register H (TDRH)
Transmit Data Register L (TDRL)
Transmit Data Register HL (TDRHL)
The TDRH and TDRL registers are 8-bit registers that store transmit data. Use these registers when asynchronous mode
and 9-bit data length are selected.
The TDRL register is the shadow register of the TDR register; i.e. access to the TDRL register is equivalent to access to
the TDR register.
When empty space is detected in the TSR register, the transmit data stored in the TDRH and TDRL registers is
transferred to the TSR register; i.e., transmitting is started.
The TSR, TDRH and TDRL registers have a double-buffered construction to realize continuous reception. When the
next data to be transmitted is stored in the TDRL register after one frame of data has been transmitted, the transmitting
operation is continued by transfer to the TSR register.
The CPU can read and write to the TDRH and TDRL registers. Bits 0 to 7 in the RDRH register are fixed to 1. These bits
are read as 1. The write value should be 1.
Writing transmit data to the TDRH and TDRL registers should be performed only once in the order from the TDRH
register to the TDRL register when a transmit data empty interrupt (TXI) request is issued.
The TDRHL register can be accessed in 16-bit units.
33.2.6 Transmit Shift Register (TSR)
The TSR register is a shift register that transmits serial data.
To perform serial data transmission, the SCI first automatically transfers transmit data from the TDR register to the TSR
register, and then sends the data to the TXDn pin.
The TSR register cannot be directly accessed by the CPU.
Address(es): SCI1.TDRH 0008 A02Eh, SCI5.TDRH 0008 A0AEh, SCI8.TDRH 0008 A10Eh, SCI12.TDRH 0008 B30Eh
Address(es): SCI1.TDRL 0008 A02Fh, SCI5.TDRL 0008 A0AFh, SCI8.TDRL 0008 A10Fh, SCI12.TDRL 0008 B30Fh
Address(es): SCI1.TDRHL 0008 A02Eh, SCI5.TDRHL 0008 A0AEh, SCI8.TDRHL 0008 A10Eh, SCI12.TDRHL 0008 B30Eh
TDRHL
TDRH TDRL
b7 b6 b5 b4 b3 b2 b1 b0 b7 b6 b5 b4 b3 b2 b1 b0
Value after reset:
1111111111111111