Method for organizing state machine by selectively grouping status signals as inputs and classifying commands to be executed into performance sensitive and nonsensitive categories

• US 5,375,248 A
• Filed: 07/29/1993
• Issued: 12/20/1994
• Est. Priority Date: 10/05/1990
• Status: Expired due to Term

• Current Assignee: Bull HN Information Systems Incorporated (Atos SE)
• Original Assignee: Bull HN Information Systems Incorporated (Atos SE)
• Inventors: Lemay, Richard A., Woods, William E., Tague, Steven A.
• Primary Examiner(s): Lee, Thomas C.
• Assistant Examiner(s): AN, MENG AI T
• Application Number:
  US08/099,117
• Time in Patent Office: 509 Days
• Field of Search: 395/800, 395/375, 395/650, 364/200
• US Class Current: 713/600
• CPC Class Codes: G06F 9/261 Microinstruction address formation
• CPC Class Codes: G06F 9/28 Enhancement of operational speed, e.g. by using several microcontrol devices operating in parallel

Abstract

A virtual memory unit (VMU) includes a state machine for controlling its operations in response to commands received from another unit. The state machine includes a plurality of programmable array logic (PAL) devices which are connected to gather status from the different sections of the unit. The outputs of the PAL devices connect in common and supply a first address input to an addressable state memory. The state memory includes a plurality of locations, each of which stores a binary code defining a different machine state. The state memory locations are accessed as a function of the status signals and current state and used in turn to generate the required subcommands for executing the received commands. The state machine makes it possible to easily classify the received commands to their complexity and urgency in terms of their effect on overall system performance.

Claims

1. A method of organizing a state machine for controlling the operations of a unit, said unit including a plurality of functional sections which generate status signals characteristic of particular operations being performed by said plurality of functional sections during different cycles of operation in response to commands received by said unit from another unit, said method comprising:

(a) classifying said commands into performance sensitive and performance nonsensitive categories according to what impact that said commands have on the operation of said unit;

(b) further classifying commands in said performance sensitive category into subcategories on the basis of number of cycles required for execution when status signals are present indicating that all essential information is present and that predetermined criteria have been met;

(c) assigning individual sequences of states within a state memory containing a plurality of addressable locations storing binary codes specifying different ones of said states for completing the execution of the operations specified by each of said subcategories of said commands within said required number of cycles;

(d) consolidating said status signals into a plurality of groups for indicating when all of said essential information is present and said predetermined criteria have been met; and

,

(e) utilizing one of said groups of the status signals of step (d) selected in accordance with current state of said unit defined by a binary code read out from the state memory location during a most recent cycle of operation, for generating one part of a composite address which further includes said current binary state code to define a next state of said unit which corresponds to the next binary code read out from one of said plurality of locations specified by all of the parts of said composite address.

2. A method of organizing a state machine for controlling the operations of a first unit in response to commands received from another unit, said first unit including a plurality of functional sections which generate status signals indicative of the operations being performed by said functional sections in response to said commands during different cycles of operation of said first unit, said method comprising:

(a) selecting a consolidated group of status signals relating to the operations of a number of said functions sections for application as inputs to said state machine;

(b) classifying said commands into performance sensitive and performance nonsensitive categories according to what impact said commands have on the operation of said first unit;

(c) further classifying said performance sensitive category of commands into subcategories on the basis of number of cycles required for executing each of said commands when all of the essential information required for completing command execution is present;

(d) assigning a first state of said state machine to commands which are classified in a first subcategory requiring a minimum number of cycles for execution;

(e) assigning said first state and a minimum number of other states to commands which are classified in a second subcategory corresponding to other ones of said commands which require a next minimum number of cycles for execution;

(f) assigning a plurality of other states corresponding to the number of cycles required to perform commands in said performance nonsensitive category in a manner so as not to cause any delay in the execution of the performance sensitive commands; and

,

(g) cycling said state machine to start in said first state and complete execution of said commands in said first and second subcategories by sequencing through said first state and a minimum number of other states when said essential information is present and by sequencing through additional states each time when essential information is not present and returning to said first state to try again to execute said command within said minimum number of cycles.