UPD784938 Datasheet, PDF (497/733 Pages) NEC – 16-Bit Single-Chip Microcontrollers

CHAPTER 20 IEBus CONTROLLER
[Supplementary explanation of overrun error]
(1) If overrun occurs during individual communication reception, resulting in frame end
If DR read is not performed following the overrun status and data retransmission reaches the maximum number
of data transfer bytes (32 bytes), a frame end interrupt (INTIE2) occurs. The overrun status is maintained until
DR read is performed even after frame end.
(2) If the next reception starts in the case of (1) above, or if the next transmission starts without DR read
being performed, following reception of the last data, regardless of whether it is broadcasting or
individual communication
Even if communication is started to one’s own address in the overrun status, an overrun caused NACK return
does not occur during the ACK period in each of the slave address, control, and telegraph length fields. However,
when DR read is not performed until data reception completion in the data field, no acknowledge is returned
and reception is not performed (DR update is not performed). If the next communication is not directed to one’s
own address, DR is not updated until DR read is performed. Since the communication is not directed at one’s
own address, data interrupt (INTIE1) or communication error interrupt (INTIE2) is not generated.
Preliminary User’s Manual U13987EJ1V0UM00
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