[comp.arch] VME bus spec ambiguous ?

sj@diab.se (Stefan Johansson) (10/03/88)

I am currently involved in the design of a VMEbus module that should include
a requester with the FAIR capability as described in ANSI/IEEE Std 1014-1987.

My problem is that I have not been able to interpret Rule 3.14 in ANSI/IEEE
Std 1014-1987 unambiguously.
I have also not been able to figure out how requesters designed according to
Rule 3.14 could be compatible with requesters of the ROR type as indicated in
Observation 3.18 in ANSI/IEEE Std 1014-1987.

If a FAIR requester receives a true DEVICE WANTS BUS signal, should it then
start looking for a high on BBSY* and a high on its bus request line before
issuing a bus request or should it just sample in a flip-flop its bus request
line when BBSY* is detected high and later use the stored value before
deciding on issuing a bus request?
-- 
Stefan Johansson,  Diab Data AB
SNAIL: Box 2029, S-183 02 Taby, Sweden
ANALOG: +46 8-7680660
EMAIL: sj@diab.se , mcvax!enea!diab!sj