Chapter 5 Mailbox; Can A Mailbox Be Set Straddling Over The Boundary Of A 64 Kb Area; When Does The Mailbox Become Full And How Is Transmission/Reception Stopped - NEC mPD98409 Q&A

Q.5.1

Can a mailbox be set straddling over the boundary of a 64 KB area?

A.5.1
No, it cannot. A mailbox must fit into the area of 64 KB set by the MSH register (the higher 16 bits of the mailbox
start address). If the mailbox is used at the maximum size (about 64 KB), the MSL register must be cleared to 0.
System memory
XXX10000h
Mailbox
XXX20000h
OK
Reference: µ PD98409 User's Manual 5.3.1 Setting of mailbox
Q.5.2

When does the mailbox become full and how is transmission/reception stopped?

A.5.2
The mailbox full notice is issued when the corresponding indication has been correctly written to the mailbox
making it full. Transmission/reception is stopped when an attempt is made to write the next indication to the full
mailbox.
Reference: µ PD98409 User's Manual 5.3.2 Operation of mailbox

CHAPTER 5 MAILBOX

64 KB boundary XXX10000h
XXX20000h
64 KB boundary
Information S14769EJ1V0IF00
System memory
64 KB boundary
Mailbox
64 KB boundary
NG
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