CHAPTER 10 SERIAL INTERFACE FUNCTION
User’s Manual U13850EJ4V0UM
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(3) Communication operations
(a) Data format
As shown in Figure 10-43, the format of the transmit/receive data consists of a start bit, character bits, a
parity bit, and one or more stop bits.
Asynchronous serial interface mode register n (ASIMn) is used to set the character bit length, parity
selection, and stop bit length within each data frame (n = 0, 1).
Figure 10-43. 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 lower 7 bits (from bit 0 to bit 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.
Asynchronous serial interface mode register n (ASIMn) and baud rate generator control register n (BRGCn)
are used to set the serial transfer rate (n = 0, 1).
If a receive error occurs, information about the receive error can be recognized by reading asynchronous
serial interface status register n (ASISn).