Commodore Amiga A500 - 100 Pin Expansion Signals

Section 3.4
100 Pin Expansion Signals on Amiga Computers
INTRODUCTlON
This section details the signals found on the 100 pin standard Amiga
expansion connector. The main point of
this document is to discuss
the signals found on the B2000 computer and how these differ from
the similar signals found on A2000 computers and those of the
original Zorro specification and A1 000 computers. Anytime some-
thing is specified for the
A2000, it is also true for the B2000 unless
otherwise stated.
Changes from Previous
We've attempted to keep the Expansion Bus pin specification as
Documents
much the same as possible from machine to machine. However, es-
pecially concerning the changes from the original specification to the
A2000 specifications, there were indeed some major changes made.
Although these changes will affect relatively few boards, they're
non-
trivial for the boards that they do affect. In this case, we basically
chose to sacrifice a small fraction of our compatibility for a reason-
ably large increase in the power of the Expansion Bus. If possible,
add-on boards should be designed for the Expansion Bus. While the
86 pin slot is similar to the A1 000 86 pin edge connector, it is in-
tended for add-on processors, such as 68020 boards. Hard disk,
memory, peripheral boards, etc. should
workjust fine in 100 pin ex-
pansion slots; the differences should only affect some
coprocessor/
turbo boards. Also note that the autoconfiguration should be done in
the 100 pin slots.
Most of the Expansion Bus signals are buffered (the ZORRO detail
will of course depend on the design; the characteristics assumed here
will be present if the Commodore-Amiga design specifications are
followed). This is an important point to keep in mind, for buffered
signals should be specifically considered in any timing analysis, while
unbuffered signals should be considered specifically in any loading
analysis. Buffered signals are typically either inputs or some synchro-
nous bidirectionals; outputs and asynchronous bidirectionals can't
easily be buffered.
Definition of Terms
Several terms are used in the following text, and an understanding of
them is required to speak proper Amiga-ese. A
PIC, or Plug In Card,
is a device that plugs into an expansion slot and follows the auto-con-
figuration protocol. Nothing should plug into a 100 pin slot that
doesn't follow
this protocol. The term slot refers to a physical plug-
in location, either the Coprocessor Slot or one of the five available
Expansion Slots. The terms
100 Pin Slot and Expansion Slot are con-
sidered synonyms, and describe one of the five 100 pin Expansion
Slots. The
Expansion Bus is the processor bus that is in common be-