NEC PD78F9488 - Manual (Page 209)

CHAPTER 11 SERIAL INTERFACE 20
User’s Manual U15331EJ4V1UD
209
(f) Reading receive data
When the reception completion interrupt (INTSR20) occurs, receive data can be read by reading the
value of receive buffer register 20 (RXB20).
To read the receive data stored in receive buffer register 20 (RXB20), read while reception is enabled
(RXE20 = 1).
Remark However, if it is necessary to read receive data after reception has stopped (RXE20 = 0), read
using either of the following methods.
(a) Read after setting RXE20 = 0 after waiting for one cycle or more of the source clock
selected by BRGC20.
(b) Read after bit 2 (DIR20) of serial operation mode register 20 (CSIM20) is set (1).
Program example of (a) (BRGC20 = 00H (source clock = fx/2))
INTREX:
;
NOP
;2 clocks
CLR1 RXE20
;Reception stopped
MOV A, RXB20 ;Read receive data
Program example of (b)
INTRXE:
;
SET1 CSIM20.2
;DIR20 flag is set to LSB first
CLR1 RXE20 ;Reception stopped
MOV A, RXB20
;Read receive data