Re: Question about 68K Bus Arbitration

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Posted by John Chappel on April 26, 1998 at 07:48:02:

In Reply to: Question about 68K Bus Arbitration posted by David Lie on April 25, 1998 at 10:46:29:

: I was wondering what happens if two devices try to
: go for the bus simultaneously by bringing BGACK low.
: As I understand it, BR is a shared request line, so
: both devices may pull it low and the CPU will not know
: there are two devices requesting the line. Now if BG
: is daisy chained, how come we did not have to explicitly
: pass the BG on if we were not requesting the BUS?
: If it is not chained then do all devices see the same
: BG line? If so, is there a possibility of collision?

: Thanks in advance

Bus Grant is daisy chained in a 68K system. In the lab we
assumed that you were the only device on the bus.

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Comments:
: : I was wondering what happens if two devices try to : : go for the bus simultaneously by bringing BGACK low. : : As I understand it, BR is a shared request line, so : : both devices may pull it low and the CPU will not know : : there are two devices requesting the line. Now if BG : : is daisy chained, how come we did not have to explicitly : : pass the BG on if we were not requesting the BUS? : : If it is not chained then do all devices see the same : : BG line? If so, is there a possibility of collision? : : Thanks in advance : Bus Grant is daisy chained in a 68K system. In the lab we : assumed that you were the only device on the bus. : JC

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