NEC UPD789026 Series, User Manual

Page: 139 / 213

CHAPTER 9 SERIAL INTERFACE 00
User's Manual U11919EJ3V0UM00
139
(2) Communication operation
(a) Data format
The transmit/receive data format is as shown in Figure 9-7. One data frame consists of a start bit,
character bits, parity bit, and stop bit(s).
The specification of character bit length, parity selection, and specification of stop bit length for one
data frame is carried out with asynchronous serial interface mode register 00 (ASIM00).
Figure 9-7. Asynchronous Serial Interface Transmit/Receive Data Format
D0 D1 D2 D3 D4 D5 D6 D7
Parity
Bit
Stop Bit
Start
Bit
One Data Frame
•
Start bit...................... 1 bit
•
Character bits............ 7 bits/8 bits
•
Parity bit .................... Even parity/odd parity/0 parity/no parity
•
Stop bit(s).................. 1 bit/2 bits
When 7 bits are selected as the number of character bits, only the low-order 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 ASIM00 and baud rate generator control register 00
(BRGC00).
If a serial data receive error is generated, the receive error contents can be determined by reading the
status of asynchronous serial interface status register 00 (ASIS00).
www.DataSheet4U.com