Asynchronous Serial Interface Transmit/Receive Data Format - NEC PD78076 User Manual

(2) Communication operation
(a) Data format
The transmit/receive data format is shown in Figure 20-7.
Figure 20-7. Asynchronous Serial Interface Transmit/Receive Data Format
Start
Bit
One data frame consists of the following bits.
• Start bit ...................
• Character bits .........
• Parity bit ..................
• Stop bit(s) ...............
The specification of character bit length, parity selection, and specification of stop bit length for each
data frame is carried out with asynchronous serial interface mode register (ASIM).
When 7 bits are selected as the number of character bits, only the lower 7 bits (bits 0 to 6) are valid;
in transmission the most significant bit (bit 7) is ignored, and in reception the most significant bit (bit
7) is always "0".
The serial transfer rate is selected by ASIM and the baud rate generator control register (BRGC).
If a serial data receive error is generated, the receive error contents can be determined by reading the
status of the asynchronous serial interface status register (ASIS).
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CHAPTER 20 SERIAL INTERFACE CHANNEL 2
One Data Frame
D0 D1 D2 D3 D4 D5
Character Bit
1 bit
7 bits/8 bits
Even parity/odd parity/0 parity/no parity
1 bit/2 bits
Parity
D6 D7 Stop Bit
Bit