UPD78F9234MC-5A4-A Datasheet, PDF (190/419 Pages) Renesas Technology Corp – Old Company Name in Catalogs and Other Documents

CHAPTER 11 SERIAL INTERFACE UART6
(1) Receive buffer register 6 (RXB6)
This 8-bit register stores parallel data converted by receive shift register 6 (RXS6).
Each time 1 byte of data has been received, new receive data is transferred to this register from receive shift
register 6 (RXS6). If the data length is set to 7 bits, data is transferred as follows.
• In LSB-first reception, the receive data is transferred to bits 0 to 6 of RXB6 and the MSB of RXB6 is always 0.
• In MSB-first reception, the receive data is transferred to bits 7 to 1 of RXB6 and the LSB of RXB6 is always 0.
If an overrun error (OVE6) occurs, the receive data is not transferred to RXB6.
RXB6 can be read by an 8-bit memory manipulation instruction. No data can be written to this register.
Generation of reset signal sets this register to FFH.
Caution Reception enable status is entered, after having set RXE6 to 1 and one clock of the base clock
(fXCLK6) has elapsed.
(2) Receive shift register 6 (RXS6)
This register converts the serial data input to the RXD6 pin into parallel data.
RXS6 cannot be directly manipulated by a program.
(3) Transmit buffer register 6 (TXB6)
This buffer register is used to set transmit data. Transmission is started when data is written to TXB6.
If the data length is set to 7 bits:
• In LSB-fast transmission, data is transferred to bits 0 to 6 of TXB6, and the MSB of TXB6 is not transmitted.
• In MSB-fast transmission, data is transferred to bits 7 to 1 of TXB6, and the LSB of TXB6 is not transmitted.
This register can be read or written by an 8-bit memory manipulation instruction.
Generation of reset signal sets this register to FFH.
Cautions 1. When starting transmission, write transmit data to TXB6, after having set TXE6 to 1 and a
wait of one clock or more of the base clock (fXCLK6) has been performed.
2. Do not write data to TXB6 when bit 1 (TXBF6) of asynchronous serial interface transmission
status register 6 (ASIF6) is 1.
3. Do not refresh (write the same value to) TXB6 by software during a communication
operation (when bit 7 (POWER6) and bit 6 (TXE6) of asynchronous serial interface operation
mode register 6 (ASIM6) are 1 or when bit 7 (POWER6) and bit 5 (RXE6) of ASIM6 are 1).
When outputting same values in continuous transmission, be sure to confirm that TXBF6 is
0 before writing the same values to TXB6.
(4) Transmit shift register 6 (TXS6)
This register transmits the data transferred from TXB6 from the TXD6 pin as serial data. Data is transferred from
TXB6 immediately after TXB6 is written for the first transmission, or immediately before INTST6 occurs after one
frame was transmitted for continuous transmission. Data is transferred from TXB6 and transmitted from the TXD6
pin at the falling edge of the base clock.
TXS6 cannot be directly manipulated by a program.
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User’s Manual U17446EJ5V0UD