Method and apparatus for communicating between master and slave electronic devices where the slave device may be hazardous

摘要

A master device (11) can access slave devices (12) either speculatively or non-speculatively. The slave devices (12) can be either non-hazardous devices or hazardous devices which exhibit status changes on reading. The master device (11) issues an access request including information as to whether the request is speculative or non-speculative, the slave device (12) then responds to the master device (11) with a negative acknowledgment that access is denied if the access request is speculative and the slave device (12) is hazardous. Otherwise, if the slave device (12) can deal with the request, a positive acknowledgment is sent. If the master device (11) receives a negative acknowledgment, it continues to reissue updated access requests until a positive acknowledgment is received. <IMAGE>