Path: utzoo!utgpu!attcan!uunet!husc6!uwvax!oddjob!rfl
From: rfl@oddjob.UChicago.EDU (Bob Loewenstein)
Newsgroups: comp.sys.mac.programmer
Subject: NuBus card design
Message-ID: <14980@oddjob.UChicago.EDU>
Date: 4 Aug 88 16:03:00 GMT
Organization: U of Chicago - Astronomy & Astrophysics
Lines: 22

We are designing an interface between CCD camera electronics
and the macII via NuBus.  The CCD readout electronics requires
that 1.5Mb of data be transferred in 2 byte segments, and each
2 bytes must be handled within 25 microseconds.  All communication
with CCD electronics is done over serial lines, and we have 
designed circuitry for parallel-serial and serial-parallel
conversion.

We need to know whether the macII mother board can be operated
in a tight software loop, avoiding interrupts and locking the
NuBus, so that it can slave our interface card in a slot and
pick up two bytes of data every 25 microseconds.  Alternatively,
what is the feasability of designing an interface card that could
become master and lock the bus to write directly to memory in
the motherboard?

We are also interested in knowing about any bare-bones, generic
interface circuitry for the MacII - NuBus, including declaration
ROM, slot decoding, and simple handling of NuBus transactions
and arbitration signals.

Any suggestions/help would be appreciated.