Register Descriptions; Receive Shift Register (Rsr); Receive Data Register (Rdr) - Renesas H8S Series Hardware Manual

15.3

Register Descriptions

The SCI has the following registers for each channel. Some bits in the serial mode register (SMR),
serial status register (SSR), and serial control register (SCR) have different functions in different
modesnormal serial communication interface mode and smart card interface mode; therefore,
the bits are described separately for each mode in the corresponding register sections.

• Receive shift register (RSR)

• Receive data register (RDR)

• Transmit data register (TDR)
• Transmit shift register (TSR)
• Serial mode register (SMR)
• Serial control register (SCR)
• Serial status register (SSR)
• Smart card mode register (SCMR)
• Bit rate register (BRR)
• Keyboard comparator control register (KBCOMP)*
Note: * KBCOMP is available in SCI_1.
15.3.1 Receive Shift Register (RSR)
RSR is a shift register used to receive serial data that converts it into parallel data. When one
frame of data has been received, it is transferred to RDR automatically. RSR cannot be directly
accessed by the CPU.
15.3.2 Receive Data Register (RDR)
RDR is an 8-bit register that stores receive data. When the SCI has received one frame of serial
data, it transfers the received serial data from RSR to RDR where it is stored. After this, RSR can
receive the next data. Since RSR and RDR function as a double buffer in this way, continuous
receive operations be performed. After confirming that the RDRF bit in SSR is set to 1, read RDR
for only once. RDR cannot be written to by the CPU. The initial value of RDR is H'00.
Section 15 Serial Communication Interface (SCI, IrDA)
Rev. 3.00 Jul. 14, 2005 Page 431 of 986
REJ09B0098-0300