NEC PD78214 - Manual (Page 362)

333
Chapter 12 Interrupt Functions
12
Ring control?
Decrement ring counter
Ring counter = 0?
Vectored interrupt request occurs
No
No
Yes
No
Subtract modulo register contents from
low-order 8-bits of macro service pointer
for data (MPDL) and return pointer to
the first address
MSC = 0?
1
Yes
Reload modulo register contents to ring counter
End
Reset interrupt request flag
End
Yes
MSC ←MSC – 1