Zilog Z16C35 - Manual (Page 215)

Application Note
The Zilog Datacom Family with the 80186 CPU
9-5
8
The three LSBs of the above MMCS values are 111 so that
the longest possible Reset pulse is generated when any of
the locations in the indicated range are accessed.
Note that if this feature is not needed, it can be disabled by
simply not programming the MMCS register.
Interrupt Daisy Chain (Priority) Order
Jumper block J25 selects whether the (E)SCC device is at
the start or the end of the interrupt daisy chain.
This variability is provided in part because early versions
of the 85230 ESCC had trouble passing an interrupt
acknowledge down the daisy chain if it occurred in response to a lower-priority device’s request just as the
ESCC was starting to make its own request. Current
85230’s don’t have the problem.
Table 6. Address Ranges for Reset
RAM Size MMCS value
Address Range for which ISCC,
IUSC, and (M)USC are Reset:
32K x 8 3BFF 3B000-3B7FF
128K x 8 DBFF DB000-DB7FF
To make the interrupt priority be: Jumper J25 as follows:
(E)SCC highest, IUSC, ISCC, (M)USC lowest J25-J2 to J25-J3, J25-J4 to J25-J5 (J25-J1, J25X open)
IUSC highest, ISCC, MUSC, (E)SCC lowest J25-J1 to J25-J2, J25-J to J25-J4 (J25-5J, J25X open)
IUSC highest, ISCC, USC, (E)SCC lowest J25X to J25-J2, J25-J3 to J25-J4 (J25-J1, J25-J5 open)
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