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From: louis@asterix.drev.dnd.ca (Louis Demers)
Newsgroups: comp.sys.mac.programmer
Subject: Surviving a Bus Error
Keywords: nubus,io,bus error, exception,interrupt
Message-ID: <1990Mar13.192544.1617@asterix.drev.dnd.ca>
Date: 13 Mar 90 19:25:44 GMT
Organization: DREV, Defence Research Est. Valcartier
Lines: 38

Hi,

Background:
	We are developing a piece of lab equipment which is controlled by
	a Macintosh  II.  We developed our own controllers which will be
	interfaced to the mac using GreenSpring IO card and some custom
	Industry Pack.  The control registers can be configured at
	different addresses.

Problems:
	When we access one of the registers and the controllers is not
	turned on, we crash with a bus errors.  We suffer the same faith
	when we access the registers at the wrong address.

Wish:
	I wish I could try to access an address and if the controller
	were turned off or not at this particular address, I would like to
	tell the user to check the power to the card or the address
	configuration.  This could take the form of a subroutine with
	could be declared like this:
			int TryIT(Ptr memoryAddress,long *value)
	the return value could indicate if the access was successful and
	the parameter value could returned the actual value read.

Question:
	Anybody has suggestions or better yet, code to do this ?
	Can it be done only in C ? I work with MPW 3.0 C and C++.
	( I hate assembler but I feel like this time I won't be able to
	avoid it &-)
	
	Thanks in advance,
		Louis

-- 
| Louis Demers              | DREV, Defence Research Establishment,Valcartier |
| louis@asterix.drev.dnd.ca | POBox 8800, Courcelette,Quebec, CANADA, G0A 1R0 |
|            (131.132.48.2) | Office: (418) 844-4424       fax (418) 844-4511 |
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