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CHAPTER 14 SERIAL INTERFACE UART
(2) Communication operations
(a) Data format
As shown in Figure 14-6, the format of the transmit/receive data consists of a start bit, character bits, a parity
bit, and one or more stop 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.
Figure 14-6. 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
• 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
When “7 bits” is selected as the number of character bits, only the low-order 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).
Summary of Contents for mPD780973 Series
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