NEC mPD780852 Series, Preliminary User'S Manual

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CHAPTER 13 SERIAL INTERFACE UART
Preliminary User’s Manual U14581EJ3V0UM00
(2) Communication operations
(a) Data format
Figure 13-6 shows the transmit/receive data format.
Figure 13-6. Format of Transmit/Receive Data in Asynchronous Serial Interface
D0 D1 D2 D3 D4 D5 D6 D7
Start
bit Parity
bit Stop bit
1 data frame
Character bits
One data frame consists of the following each bit.
• Start bit ............. 1 bit
• Character bits ... 7 bits or 8 bits
• Parity bit ........... Even parity, odd parity, zero parity, or no parity
• Stop bit(s) ........ 1 bit or 2 bits
The asynchronous serial interface mode register (ASIM) is used to set the character bit length, parity
selection, and stop bit length within each data frame.
When “7 bits” is selected as the number of character bits, only the lower 7 bits (bits 0 to 6) are valid, so that
during a transmission the highest bit (bit 7) is ignored and during reception the highest bit (bit 7) must be
set to “0”.
The asynchronous serial interface mode register (ASIM) and the baud rate generator control register (BRGC)
are used to set the serial transfer rate.
If a receive error occurs, information about the receive error can be recognized by reading the asynchronous
serial interface status register (ASIS).