NEC UPD789026 Series User Manual page 143

(e) Receive errors
Receive Error
Parity error
Framing error
Overrun error
RxD (Input)
RxD (Input)
www.DataSheet4U.com
CHAPTER 9 SERIAL INTERFACE 00
The following three errors may occur during a receive operation: a parity error, framing error, or
overrun error. Upon data reception, an error flag is set in asynchronous serial interface status register
00 (ASIS00). Receive error causes are shown in Table 9-7.
It is possible to determine what kind of error was generated during reception by reading the contents of
ASIS00 in the reception error interrupt servicing (see Figures 9-9 and 9-10).
The contents of ASIS00 are reset to 0 by reading receive buffer register 00 (RXB00) or receiving the
next data (if there is an error in the next data, the corresponding error flag is set).
Transmission-time parity specification and reception data parity do not match
Stop bit not detected
Reception of next data is completed before data is read from receive buffer register
START
INTSR
(b) Framing error or overrun error generated
START
INTSR
Cautions 1. The contents of the ASIS00 register are reset to 0 by reading receive buffer register
00 (RXB00) or receiving the next data.
ASIS00 before reading RXB00.
2. Be sure to read receive buffer register 00 (RXB00) even if a receive error is
generated. If RXB00 is not read, an overrun error will be generated when the next
data is received, and the receive error state will continue indefinitely.
Table 9-7. Receive Error Causes
Figure 9-10. Receive Error Timing
(a) Parity error generated
D0 D1 D2
D0 D1 D2
User's Manual U11919EJ3V0UM00
Cause
STOP
D6 D7 Parity
STOP
D6 D7 Parity
To ascertain the error contents, read
143