NEC NEC PD78081(A), User Manual

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CHAPTER 11 SERIAL INTERFACE CHANNEL 2
(2) Communication operation
(a) Data format
The transmit/receive data format is as shown in Figure 11-7.
Figure 11-7. Asynchronous Serial Interface Transmit/Receive Data Format
1 Data frame is configured from the following bits.
• Start bits .................. 1 bit
• Character bits ......... 7 bits/8 bits
• Parity bits ................ Even parity/odd parity/0 parity/no parity
• Stop bit(s) ............... 1 bit/2 bits
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 means of the 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).
D0 D1 D2 D3 D4 D5 D6 D7
Parity
Bit
Stop Bit
Start
Bit
One Data Frame
Character Bit