IO adapter for system and IO buses having different protocols and speeds

• US 5,191,653 A
• Filed: 12/28/1990
• Issued: 03/02/1993
• Est. Priority Date: 12/28/1990
• Status: Expired due to Term

• Current Assignee: Apple Inc.
• Original Assignee: Apple Computer Incorporated (Apple Inc.)
• Inventors: Scalise, Albert M., Karakotsios, Kenneth M., Banks, John D. (J.)
• Primary Examiner(s): Anderson, Lawrence E.
• Application Number:
  US07/635,923
• Time in Patent Office: 795 Days
• Field of Search: 395/325, 395/725, 395/550
• US Class Current: 710/113
• CPC Class Codes: G06F 13/4027 using bus bridges G06F13/4022 takes precedence

Abstract

A bi-directional bus adapter coupling a system bus, which operates at a first speed using a first protocol, and an IO bus, which operates at a second speed using a second protocol, and allowing data transfering devices on either bus to transfer data to or from devices on the other bus. The bus adapter includes a cycle generation mechanism which is responsive to data cycles from one of the buses in order to generate bus cycles needed to complete a data transfer to a device on the other bus. The bus adapter includes a synchronization mechanism for converting the plurality of data cycles generated by the cycle generation mechanism from either the first speed to the second speed or vice versa. The bus adapter includes bi-directional data path mechanism for routing data between the system and IO buses according to said protocols, such that the data path directs bytes of data to specific data lines to perform byte steering and dynamic bus sizing on the data from the system bus to the IO bus. The bus adapter also includes a bi-directional address transceiver mechanism for routing addresses between said system and said IO buses.

Claims

1. A bi-directional bus adapter coupled between first and second buses, said buses consisting of data, address an control lines, said first and second buses containing a plurality of first and second data transferring devices, each generating a first plurality of data cycles designed to send and receive data according to a predetermined databus size, said first and second buses operating at first and second speeds respectively with first and second bus control protocols respectively, said first and second speeds and first and second bus control protocols being different, said bus adapter provided to allow said devices coupled to either of said buses to transfer data to other devices contained on the other of said buses, said bus adapter comprising:

arbitration means responsive to said plurality of data cycles from said devices, said arbitration means for determining ownership based upon priority of both said first and second buses by only one of said devices at any one time, wherein said arbitration means supports said first and second bus control protocols;

bus cycle generation means, responsive to said first plurality of data cycles from one of said devices on one of said buses, for generating a second plurality of data cycles necessary to complete said data transfer to one of said other devices on the other of said buses, such that the bus control protocols of each of said buses is supported during said data transfer;

synchronization means coupled to said bus cycle generation means for converting said second plurality of data cycles from either said first speed to said second speed or said second speed to said first speed;

bi-directional data path means coupled between said data bus of said first bus and said databus of said second bus and responsive to said first plurality of data cycles, said data path for performing data path routing between said first and second buses according to said bus control protocols; and

bi-directional address transceiver means coupled between said databus of said first bus and said databus of said second bus and responsive to said first plurality of data cycles, said transceiver means for routing addresses between said first and said second buses,

wherein devices on either of said buses transfer data to devices on the other of said buses according to their bus control protocols, such that said first and second buses operate as one single bus.

2. The bus adapter as in claim 1 wherein said adapter operates at said first speed.

3. The adapter as in claim 1 wherein said data path apparatus performs dynamic bus sizing of said data being transferred.

4. The bus adapter in claim 1 wherein said bus cycle generation means includes:

first cycle generation means responsive to said plurality of data cycles from said system bus, said first cycle generation means for generating IO bus data cycles necessary to complete a data transfer to said IO bus;

second cycle generation means responsive to said plurality of data cycles from said IO bus, said second cycle generation means for generating system bus data cycles necessary to complete a data transfer to said system bus.

5. The bus adapter as in claim 4 wherein said synchronization means includes:

first synchronization means responsive to said plurality of data cycles from said first cycle generation means, said first synchronization means for converting said plurality of data cycles from said system bus speed to said IO bus speed;

second synchronization means responsive to said plurality of data cycles from said second cycle generation means, said second synchronization means for converting said plurality of data cycles from said IO bus to said system bus speed.

6. A bi-directional bus adapter coupled between a system bus and an IO bus, said buses consisting of data, address and control lines, said system and IO buses containing a plurality of system and IO data transferring devices, each generating a first plurality of data cycles to send and receive data according to a predetermined databus size, said system and IO buses operating at system and IO speeds respectively with system and IO protocols respectively, said system and IO speeds and system and IO protocols being different, said bus adapter provided to allow said devices coupled to either of said buses to transfer data to devices contained on the other of said buses, said bus adapter comprising:

arbitration means responsive to said plurality of data cycles from said devices, said arbitration means for determining ownership based upon priority of both said system and IO buses at any one time by only one of said devices, said arbitration means supporting said system and IO protocols;

system cycle generation means responsive to said plurality of data cycles from said IO bus for generating system bus data cycles necessary to complete a data transfer to said system bus according to said system bus protocol;

IO cycle generation means responsive to said plurality of data cycles from said system bus for generating IO bus data cycles necessary to complete a data transfer to said IO bus according to said IO bus protocol;

system synchronization means responsive to said system bus data cycles from said system cycle generation means, said system synchronization means for converting said system bus data cycles generated by said system cycle generation means from said IO bus speed to said system bus speed;

IO synchronization means responsive to said IO bus data cycles from said IO cycle generation means, said IO synchronization means for converting said IO bus data generated by said IO cycle generation means from said system bus speed to said IO bus speed;

bi-directional data path means coupled between said databus of said system bus and said databus of said IO bus and responsive to said plurality of data cycles, said data path for routing data between said system and IO buses according to said protocols, such that said data path directs bytes of said data to specific data lines to perform byte steering and dynamic bus sizing on said data from said system bus to said IO bus; and

bi-directional address transceiver means coupled between said databus of said system bus and said databus of said IO bus and responsive to said plurality of data cycles for routing addresses between said system and said IO buses,

wherein devices on either of said buses transfer data to devices on the other of said buses according to their bus protocols, such that said first and second buses operate as one single bus.

7. The bus adapter as in claim 6 wherein said system bus operates at either approximately 25 or 33 MHz and said IO bus operates at either approximately 15.6672 or 24.28416 MHz.

8. The bus adapter as in claim 6 further including timeout logic means for terminating said data cycles from one of said devices assuming ownership of said buses, wherein said timeout logic counts bus clock cycles to a predetermined number, such that said timeout logic generates a bus error where said data cycles are not acknowledge by the time said timeout logic counts to said predetermined number.

9. The bus adapter as in claim 6 wherein said system and IO buses are a system bus with a processor and an IO bus without a processor respectively.

10. A bi-directional bus adapter coupled between a system bus and an IO bus, said system bus operating at either approximately 25 or 33 MHz and containing a processor, said IO bus operating at either approximately 15,6672 or 24.28416 MHz, said buses consisting of data, address and control lines, said system and IO buses containing a plurality of system and IO data transferring devices, each generating a first plurality of data cycles to send and receive data according to a predetermined data bus size, said system and IO buses operating at system and IO speeds respectively with system and IO protocols respectively, said system and IO speeds and system and IO protocols being different, said bus adapter provided to allow said devices coupled to either of said buses to transfer data to devices contained on the other of said buses, said bus adapter comprising:

arbitration means responsive to said plurality of data cycles from said devices, said arbitration means for determining ownership based upon priority of said system and IO buses by only one of said devices at any given time;

system cycle generation means responsive to said plurality of data cycles from said IO bus for generating system bus data cycles necessary to complete a data transfer to said system bus according to said system bus protocol;

IO cycle generation means responsive to said plurality of data cycles from said system bus for generating IO bus data cycles necessary to complete a data transfer to said IO bus according to said IO bus protocol;

system synchronization means responsive to said system bus data cycles from said system cycle generation means, said system synchronization means for converting said system bus data cycles generated by said system cycle generation means from said IO bus speed to said system bus speed;

IO synchronization means responsive to said IO bus data cycles from said IO cycle generation means, said IO synchronization means for converting said IO bus data cycles generated by said IO cycle generation means from said system bus speed to said IO bus speed;

bi-directional data path means coupled between said databus of said system bus and said data bus of said IO bus and responsive to said plurality of data cycles, said data path for routing data between said system and IO buses according to said protocols, such that said data path directs bytes of said data to specific data lines to perform byte steering and dynamic bus sizing on said data from said system bus to said IO bus; and

bi-directional address transceiver means coupled between said databus of said sustem bus and said databus of said IO bus and responsive to said plurality of data cycles for routing addresses between said system and said IO buses,

wherein devices on either of said buses transfer data to devices on the other of said buses according to their bus protocols, such that said first and second buses operate as one single bus.