US 3,993,981 AGranted

Apparatus for processing data transfer requests in a data processing system

AssigneeHoneywell Information Systems Inc.

InventorsFrank V. Cassarino, Jr., George J. Barlow, George J. Bekampis, John W. Conway, Richard A. Lemay, David B. O'Keefe, Douglas L. Riikonen, William E. Woods

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Abstract

In a data processing system having a plurality of units coupled for the transfer of information therebetween over a common electrical bus during asynchronously generated information bus transfer cycles, the units are coupled in a priority network and depending upon their respective priority may gain access to the bus before a lower priority unit is so enabled. Each one of the units includes apparatus for responding to a request for the transfer of information from another unit by providing any one of up to three signal responses including a positive acknowledge signal indicating an immediate response, a negative acknowledge signal indicating that the unit will most likely be busy for a relatively extended period of time and a quasi-negative response indicating that the unit will probably be ready during the next asynchronously generated bus transfer cycle.

Claims16

Dependent claims

A data processing system comprising:

A. a plurality of units;
B. a common electrical bus;
C. means for coupling each of said units to said bus;
D. means for indicating the priority of each one of said units;
E. means, included in each of said units, for requesting the use of said bus for transfer of information to another one of said units during an asynchronously generated transfer cycle;
F. means, included in each of said units, for asynchronously generating a said transfer cycle for the requesting unit, independent of the operation of each of the other ones of said units, if the requesting unit is the highest priority unit requesting a transfer cycle;
G. means, included in the highest priority requesting unit, for enabling the transfer of information during the generated transfer cycle to another one of said units, hereinafter referred to as a receiving unit;
and
H. means, included in each of said units, for acknowledging the receipt of information from the highest priority requesting unit, hereinafter referred to as a transferring unit said means for acknowledging comprising
1. first means for generating a first signal if the receiving unit receives an indication that it is the unit to which the transferring unit is transferring the information,
2. second means for generating a second signal if the receiving unit is not busy,
3, third means, coupled to said first and second means for generating, for generating a positive acknowledgment in response to the presence of both said first and second signals, and
4. fourth means, coupled to said first and second means for generating, for generating a negative acknowledgment in response to the presence of said first signal and the absence of said second signal.

10 more elements

A data processing system comprising:

A. a plurality of units;
B. a common electrical bus, having first and second ends;
C. means for coupling each of said units to said bus, the one of said units coupled closest to said first end having the highest priority, the priority of the others of said units also based on their proximity to said first end;
D. a plurality of devices coupled with at least one of said units;
E. means, included in each of said units, for asynchronously generating a transfer cycle for the requesting unit, independent of the operation of each of the other ones of said units, if the requesting unit is the highest priority unit requesting a transfer cycle;
F. means, included in the highest priority requesting unit, for enabling the transfer of information during the generated transfer cyle to a designated device coupled with another one of said units, hereinafter referred to as a receiving unit;
and
G. means, included in some of said units, for acknowledging the transfer of information from the highest priority requesting unit, hereinafter referred to as a transferring unit, said means for acknowledging comprising:
1. first means for generating a first signal if the receiving unit receives an indication that it is the unit to which the transferring unit is transferring the information,
2. second means for generating a second signal if the receiving unit is not busy,
3. third means for generating a third signal if the designated device is not busy,
4. fourth means, coupled with said first, second and third means for generating, for generating a positive acknowledgment in response to said first, second and third signals, and
5. fifth means, coupled with said second and third means for generating, for generating a negative acknowledgment in response to the absence of either said second or third signals.

10 more elements

Dependencies are inferred from the claim text.