CAMAC SERIAL SYSTEM WITH REQUEST GRANT SERIAL CONTROLLERS.

THE STANDARD CAMAC SERIAL HIGHWAY CRATE CONTROLLER TYPE L-2 PROVIDES FOR ABRITRATION ON THE AUXILIARY CONTROL BUS (ACB) AS DEFINED IN IEEE STD 675-1979 IN ONLY THE AUXILIARY CONTROLLER LOCKOUT (ACL) MODE. ALTHOUGH THIS PROVIDES COMPATABILITY WITH OTHER CONTROLLERS DESIGNED TO USE THE ACB, THERE ARE A NUMBER OF SIGNIFICANT DRAWBACKS TO THIS TYPE OF OPERATION; 1. THE L-2 CONTROLLER MUST BE THE CONTROLLER OF HIGHEST PRIORITY. SINCE ONLY ONE CONTROLLER MAY USE ACL, OTHER CONTROLLERS MUST USE REQUEST GRANT ARBITRATION. IN MANY APPLICATIONS IT IS UNDESIRABLE TO GIVE THE L-2 CONTROLLER HIGH PRIORITY. 2. ONLY ONE CONTROLLER ON THE ACB MAY USE ACL ARBITRATION. UNDER THE PRESENT ARBITRATION SYSTEM IT IS NOT POSSIBLE TO HAVE MORE THAN ONE TYPE L-2 CONTROLLER ON THE ACB. THE USE OF MORE THAN ONE L-2 CONTROLLER IN A CAMAC CRATE HAS THE, APPLICATION OF MULTIPLE PROCESSOR ACCESS. THE INCLUSION OF A REQUEST GRANT MODE OF OPERATION IN A SERIAL CRATE CONTROLLER OF THE L-2 TYPE WOULD SIGNIFICANTLY INCREASE THE USEFULLNESS OF THE SERIAL HIGHWAY IN LARGER SYSTEMS WITH CAMAC CRATES SEPERATED BY DISTANCES WHERE THE PARALLEL BRANCH HIGHWAY IS NOT PRACTICAL. PHASE I OF THIS PROPOSAL ADDRESSES A TECHNIQUE OF INCORPORATING REQUEST GRANT ARBITRATION INTO THE SERIAL HIGHWAY AND SERIAL HIGHWAY CONTROLLERS IN A MANNER THAT WILL ALLOW R/G SERIAL CONTROLLERS AND L-2 CONTROLLERS TO OPERATE ON THE SAME SERIAL HIGHWAY.