HD6432670 Hitachi, HD6432670 Datasheet - Page 683

• Manufacturer Part Number: HD6432670
• Description: (HD64F267x Series) 16-Bit Microcomputer
• Manufacturer: Hitachi

Note: Only in H8S/2678R Series.
15.3.1
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.
15.3.2
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.
15.3.3
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.
Smart card mode register_1 (SCMR_1)
Bit rate register_1 (BRR_1)
Receive shift register_2 (RSR_2)
Transmit shift register_2 (TSR_2)
Receive data register_2 (RDR_2)
Transmit data register_2 (TDR_2)
Serial mode register_2 (SMR_2)
Serial control register_2 (SCR_2)
Serial status register_2 (SSR_2)
Smart card mode register_2 (SCMR_2)
Bit rate register_2 (BRR_2)
Serial extension mode register (SEMR)*
Receive Shift Register (RSR)
Receive Data Register (RDR)
Transmit Data Register (TDR)
Rev. 2.0, 04/02, page 637 of 906