IEBus

Regarding IEBus, if a slave reception request (SLVRQ) is received during a master transmission request (such as DR setting, MSTRQ setting), can I first finish the slave reception start processing then resume the master transmission request?

Yes, you can.
Issue a master transmission request after performing the slave reception processing.
Note, however, that the MSTRQ setting cannot be performed during a period of 61.7μs (forcible reset period) after defeat in a bus conflict.
(Refer to Caution 1 (p.562) in the manual (6th Edition).)

During slave reception, I want the other communication party to perform retransmission, without performing reception (without overwriting RAM by DMA transfer).
To achieve this, I should not take any action upon occurrence of the INTIE2, STARTF, and SLVRQ interrupts: Is this an appropriate method?

Yes, it is. However, be sure to clear the ISR flag.

When an overrun occurs and a multicast IEERR interrupt or unicast ENDFRAM interrupt occurs, is it all right to set "char dummy = DR;" to read DR (dummy read) upon occurrence of an error interrupt?

Yes.
If you want to discard the frame, you can use a dummy read.

The master transmission side acknowledges the ENDFRAM interrupt and performs retransmission during unicast communication, but abandons transmission during multicast communication.
Is this correct?

Yes, it is.

I want to completely delete ISR when the master request does not get through, after INTIE2 interrupt processing.
In this case, may I clear the STARTF or ENDTRNS flag by setting the ENSLVRX flag?

Clear STARTF by byte-writing ISR, and clear ENDTRNS by setting the ENDSLVRX flag, etc.

In this case, if the ISR register is not cleared, is it likely that STARTF and ENDTRNS will be set at the same time?

Yes it is. In the first place, the next INTIE2 is not generated when ISR is not 0.

How can I get the destination address of receive data during slave reception?
During multicast communication, is there any method for distinguishing between all-unit multicast and group-unit multicast?

You can get the address of the master, but unfortunately you cannot obtain other addresses during slave reception.
Also, you can only distinguish between multicast reception or unicast reception, but not any further.

It is stated that the IEBus controller is a "simplified version".
What is the difference between the complete version and the simplified version?
Also, is an external device required?

The complete version of the IEBus controller has a 32-byte transmit/receive buffer, but the simplified version of the IEBus controller has only a 1-byte transmit/receive buffer.
An external differential driver is required on the transmit/receive data line (not manufactured by NEC Electronics).