Texas Instruments Corporation

Jay T Cantrell

Edward R Schurig

Khodor S Elnashar

Clarence D Lewis

William Alan Saperstein

Vladimir Kljajic

Ravishankar Kodavarti

Ed Schurig

Mark A Granger

A baud clock () for use by a serial communication interface () is generated by dividing a base clock of the serial communication interface by one of a plurality of possible composite divisors (D). Each composite divisor is indicative of a minimum time interval by which adjacent pulses of the baud clock are to be separated, and further indicates that at least one pair of adjacent pulses within each symbol interval of the baud clock are to be separated by an extended time interval which is longer than the minimum time interval.

High-speed, high granularity baud clock generation

A snapshot arbiter system for servicing multiple interrupt requests for a central processing unit (CPU) in a digital processor system, and for providing interrupts to the CPU corresponding to the interrupt requests. The system includes a synchronizer adapted to synchronize interrupt requests to a clock as they are received, and an interrupt masker adapted to receive a set of indicators identifying interrupt requests to be masked and to output active indicators that are a set of active interrupt request values corresponding to received interrupt requests that are not masked. Also included is a priority encoder block adapted to receive a set of priority values for respective interrupt requests and to provide as an output priority indicators that are a set of codes representing the priority values. A snapshot enable block is included, adapted to store enable indictors that are a set of bits representing currently enabled interrupt requests, and output those bits as enable bits. Also included is a snapshot register adapted to receive the active indicators and the enable indicators, and to output snapshot indicators that are a set of values representing the currently active and enabled interrupts. An interrupt generation block is included, adapted to receive the snapshot indicators and the priority indicators, and to output an interrupt corresponding to a highest priority interrupt request, to output a highest indicator representing a highest interrupt priority level in the snapshot register, and to output for reading by the CPU an identification indicator representing a currently selected interrupt request. Finally, an interrupt preemption block is included, adapted to receive the priority indicators, the active indicators and the highest indicator, and to output to the snapshot enable block a set of bits corresponding to each current interrupt request higher in priority than all of the interrupt requests represented in the snapshot register, for updating the snapshot enable block.

Snapshot arbiter mechanism

A digital circuit (11) for compelling storage of attributes and for providing output signals indicating status of the storage of attributes, the digital circuit comprising: a digital storage device (26); a first combinational logic circuit (20) connected to the digital storage device (26) for enabling the digital storage device (26) to store the attributes based upon a set of stable first compelled inputs and an enable signal; a second combinational logic circuit (18) connected to the digital storage device for clearing the digital storage device (26) based upon a set of stable second compelled inputs and a clear signal; a first logic gate (30) connected to the digital storage device (26) and the first combinational logic circuit (20) for outputting a signal representative of the attribute being stored in the digital storage device (26); and a second logic gate (28) connected to the digital storage device (26) and the second combinational logic circuit (18) for outputting a signal representative of the digital storage device being cleared. The circuit advantageously reduces that number of states required by an asynchronous state machine without a significant performance degradation.

Asynchronous state machine attribute compeller

A method of improving efficiency in computer systems through a novel arbitration scheme is disclosed. The arbitration scheme includes a bus arbiter circuit that transparently operates in both central arbitration and distributed arbitration computer systems. The bus arbiter circuit includes an arbitration request sequencer, an arbitration competition protocol sequencer, a multiplexer, a latch, two comparators, and a series of control status registers that together provide increased system efficiency by effectively self-preempting competition priorities on its own board, thus allowing tasks with the highest priorities to compete for mastership of the bus and eliminating priority inversions.

Arbitration request sequencer

An embodiment of the present invention is a digital circuit (block 12 of FIG. 1) for interfacing between a first bus (10), which can operate synchronously or asynchronously, and a second bus (14), which can operate synchronously or asynchronously, the digital circuit comprising: compelled data decoders (40 and 50) connected to the first bus for receiving compelled data and decoding the compelled data; packet data decoders (52 and 45) connected to the first bus for receiving packet data and decoding the packet data; a digital storage device (28), preferably a FIFO comprising a plurality of write banks and a plurality of read banks or a FIFO comprising a plurality of dual-ported RAMs, having an input selectively connected to the compelled data decoders, the packet data decoders, and the second bus (via lines 44) for storing the decoded data and data from the second bus, the digital storage device additionally includes an output connected to the second bus (via lines 42) for outputting the stored decoded data to the second bus; compelled data encoders connected to the output of the digital storage device for encoding the stored data received from the second bus and outputting the encoded data to the first bus; and packet data encoders (34 and 36) connected to the output of the digital storage device for encoding the stored data received from the second bus and outputting the encoded data to the first bus. Preferably, multiple bits of data are progressively written into each write bank of the digital storage device within a clock cycle whereby the data is stored at a rate higher than the FIFO could store with a single bank. The first bus can operate synchronously or asynchronously and the second bus can also operate synchronously or asynchronously. The first and second buses can operate at different clock rates and have different data widths.

Programmable dual port data unit for interfacing between multiple buses

An improved data sampling system for sampling data transmission in a computer system includes a reference clock, a delay locked loop circuit, a packet enable circuit, a delayed selector control circuit, a sample selector, and a sample circuit. The devices may be constructed on a single semiconductor substrate and may be connected to a bus structure having a microcomputer and a plurality of boards coupled to it. The delay locked loop circuit generates accurate delayed clock signals based on the reference clock. A positive edge synchronizer circuit, within the delay locked loop, serves as a programmable phase adjust for the sampling system. The positive edge synchronizer ensures proper phase relationship between the chosen delayed clock signal and the incoming data across semiconductor process variations. Packet enable circuit informs the delayed control circuit and the sample circuit when a start bit or stop bit is initiated in a data packet and enables those circuit blocks accordingly. The delayed selector control circuit uses the delayed clock signals to detect a start bit on a data signal. The delayed selector control circuit employs the data signal, delayed appropriately, as a metastability hardener to eliminate potential metastability problems associated with coincident data and delay locked loop signal waveforms. The sample selector, in response to detection of the start bit by the delayed selector control circuit, selects two sampling signals from the delay locked loop circuit for even bit and odd bit sampling in the sample circuit.

Packet data recovery system

A system module 20 includes a processor 10, a system bus 15, a local bus 11 coupled to the processor, arbitration circuitry 12 coupled to the local bus and the system bus for providing common hardware protocol for distributed mode and central mode operations, and protocol control circuitry 13 coupled to the arbitration circuitry, the system bus, and the local bus for providing a system bus request to the arbitration circuitry when the system module desires to perform a bus transaction. The local bus 11 may be a processor bus on a system module while the system bus 15 may be an architecture bus standard such as Futurebus+. Also a method of operating arbiter circuitry in distributed mode or central mode where no change in hardware or software is needed when switching system operations between distributed and central modes.

Bus arbiter system and method utilizing hardware and software which is

A method and apparatus for a time domain boundary bridge circuit for capturing an event on an asynchronous input is described, comprising an S-R latch coupled to an asynchronous input, a first D flip-flop coupled to a synchronous clock and the output of the S-R latch, and a second D type flip-flop coupled to a synchronous clock and the output of the first D flip-flop, and having an output coupled to a circuit output terminal, operable to provide a synchronous output which reflects an event occurrence on the asynchronous input. A second embodiment is disclosed for use in systems where the asynchronous input signal is accompanied by a clock or strobe signal comprising a first D type flip-flop clocked on the strobe signal coupled to the asynchronous input signal, a second D type flip-flop clocked on a synchronous clock and coupled to the output of the first D type flip-flop, a third D type flip-flop coupled to the output of the second D type flip-flop and driving a circuit output terminal, and self clearing logic which clears the first D type flip-flop when the event is synchronously transmitted on the circuit output. A third embodiment is disclosed wherein the second embodiment additionally comprises rapid self-clearing logic improving the throughput rate possible on the asynchronous input signal. Other embodiments are also disclosed.

Time-domain boundary bridge method and apparatus

One embodiment of the present invention is a digital circuit (10) for providing glitch-free data in an asynchronous environment, the circuit comprising: an input circuit (11) for accepting data; combinational logic circuitry (12) for accepting the data from the input circuit (11 ) and manipulating the data to provide output data, wherein a delay in data flow occurs while the combinational logic manipulates the data; and an output circuit (14) for accepting the output data at a predetermined period after the receipt of data by the input circuit. Preferably, the predetermined period is at least as long as the delay in data flow.

Glitch-eliminator circuit

A method and apparatus for a circuit physically realizing a time domain boundary buffer circuit for coupling an asynchronous sequential state machine controller to an asynchronous bus interface is described. A time domain boundary bridge latch circuit comprising a latch coupled to an asynchronous input, a delay element, and further coupled to a signal from the asynchronous sequential machine so that the signal from the asynchronous bus may be reliably captured is coupled to an input of the asynchronous sequential machine. The circuitry is designed to enable the asynchronous sequential machine to sample the asynchronous input as rapidly as possible without metastability errors. A second embodiment is disclosed for coupling an asynchronous sequential machine to a plurality of data bits on an asynchronous bus interface. Additional embodiments and applications are also disclosed.

Time-domain boundary bridge method and apparatus for asynchronous

A method and apparatus for a circuit physically realizing a time domain boundary buffer circuit for capturing data signals transmitted on an asynchronous domain bus and transmitting the data signals to a synchronous domain is described. The circuit comprises a data ready circuit and a data buffer circuit. The data ready circuit comprises a first flip flop is coupled to an asynchronous input, a second flip-flop is coupled to the synchronous domain clock and the output of the first flip flop, and a third flip-flop is coupled to the synchronous domain clock and the output of the second flip-flop, the circuit having an output coupled to a circuit output terminal; the third flip flop for providing a synchronous output which reflects an event occurrence on the asynchronous input. Other embodiments are also described.

Time-domain boundary buffer method and apparatus

A glitch filter identifies and eliminates positive edge and negative edge glitches without utilizing a high frequency sampling clock. The glitch filter comprises a programmable delay buffer string, two multiple input AND gates and a latch. The buffer string provides a plurality of incrementally delayed signals and utilizes them as signal samples thus simulating a high frequency sampling clock. The two multiple input AND gates serve to eliminate positive or negative edge glitches. The latch outputs the accurate filtered data without any positive or negative edge glitches.

Growing community of inventors

Dallas, TX, United States of America

Jay T Cantrell