h8s-2172 Renesas Electronics Corporation., h8s-2172 Datasheet - Page 325

• Manufacturer Part Number: h8s-2172
• Description: Renesas 16-bit Single-chip Microcomputer H8s Family H8s-2100 Series
• Manufacturer: Renesas Electronics Corporation.

11.3
The SCI has the following registers. For details on the module stop control register, see section
16.1.2, Module Stop Control Registers H and L (MSTPCRH, MSTPCRL). To read the state of the
RxD pin, see section 8.10.3, Port A Register (PORTA).
• Receive shift register (RSR)
• Transmit shift register (TSR)
• Receive data register (RDR)
• Transmit data register (TDR)
• Serial mode register (SMR)
• Serial control register (SCR)
• Serial status register (SSR)
• Bit rate register (BRR)
11.3.1
RSR is a shift register used to receive serial data that is input to the RxD pin and convert it into
parallel data. When one byte of data has been received, it is transferred to RDR automatically.
RSR cannot be directly accessed by the CPU.
11.3.2
RDR is an 8-bit register that stores receive data. When the SCI has received one byte of serial
data, it transfers the received serial data from RSR to RDR where it is stored. After this, RSR is
receive-enabled. Since RSR and RDR function as a double buffer in this way, enables continuous
receive operations to 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.
11.3.3
TDR is an 8-bit register that stores transmit data. When the SCI detects that TSR is empty, it
transfers the transmit data written in TDR to TSR and starts transmission. The double-buffered
structures of TDR and TSR enable continuous serial transmission. If the next transmit data has
already been written to TDR during serial transmission, the SCI transfers the written data to TSR
to continue transmission. Although TDR can be read or written to by the CPU at all times, to
achieve reliable serial transmission, write transmit data to TDR for only once after confirming that
the TDRE bit in SSR is set to 1.
Register Descriptions
Receive Shift Register (RSR)
Receive Data Register (RDR)
Transmit Data Register (TDR)
Rev. 2.00, 03/04, page 293 of 534