Method and apparatus for detecting handshaking protocol errors on an asynchronous data bus
AssigneeMaxtor Corporation
InventorsBruce A. Leshay, Dana Hall
Life of this patent
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Abstract
A circuit for monitoring and detecting data transfer protocol errors that occur during asynchronous transfer of data over a data bus. The circuit monitors bus request/acknowledge control lines in accordance with a predetermined handshaking protocol. In the event that an undefined or illegal logic state is detected on the data bus request or acknowledge control lines, the circuit provides an error value to the data sending entity. As a result of receiving this error value, the data sending entity can retry the data transmission over data bus.
Claims14
A Circuit Arrangement for detecting data transfer protocol errors transmitted over a data bus between a sending unit and a receiving unit in accordance with a predetermined handshaking protocol, the bus including data lines for data transmission, a request line and an acknowledge line separate from the data lines for said handshaking protocol, the handshaking protocol on the request line and the acknowledge line having a logical sequence 11, 01, 00, 10, and returning to 11, and including a first detector circuit connected to monitor the request line for error events occurring on the acknowledge line and including a first logic circuitry for detecting a first erroneous sequence from 11 to 10, and for detecting a second erroneous sequence from 00 to 01, and for putting out an error condition indication upon detection of one of the first erroneous sequence and the second erroneous sequence.
A Circuit Arrangement for detecting data transfer protocol errors transmitted over a data bus between a sending unit and a receiving unit in accordance with a predetermined handshaking protocol, the bus including data lines for data transmission, a request line and an acknowledge line separate from the data lines for said handshaking protocol, the handshaking protocol on the request line and the acknowledge line having a logical sequence 11, 01, 00, 10, and returning to 11, and including a second detector circuit connected to monitor the acknowledge line for error events occurring on the request line and including a first logic circuitry for detecting a third erroneous sequence from 01 to 11, and for detecting a fourth erroneous sequence from 10 to 00, and for putting out an error condition indication upon detection of one of the third erroneous sequence and the fourth erroneous sequence.
A Circuit Arrangement for detecting 11 data transfer protocol errors transmitted over a data bus between a sending unit and a receiving unit in accordance with a predetermined handshaking protocol, the bus including date lines for data transmission, a request line and an acknowledge line separate from the data lines for said handshaking protocol, the handshaking protocol on the request line and the acknowledge line having a logical sequence 11, 01, 00, 10, and returning to 11, and including a first detector circuit connected to monitor the request line for error events occurring on the acknowledge line and including a first logic circuitry for detecting a first erroneous sequence from 11 to 10, and for detecting a second erroneous sequence from 00 to 01, and for putting out an error condition indication upon detection of one of the first erroneous sequence and the second erroneous sequence, and further including a second detector circuit connected to monitor the acknowledge line for error events occurring on the request line and including a first logic circuitry for detecting a third erroneous sequence from 01 to 11, and for detecting a fourth erroneous sequence from 10 to 00, and for putting out an error condition indication upon detection of one of the third erroneous sequence and the fourth erroneous sequence.
A method for detecting data transfer protocol errors transmitted over a data bus between a sending unit and a receiving unit in accordance with a predetermined handshaking protocol, the bus including data lines for data transmission, a request line and an acknowledge line separate from the data lines for said handshaking protocol, the handshaking protocol on the request line and the acknowledge line having a logical sequence 11, 01, 00, 10, and returning to 11, the method including the steps of:
- monitoring the request line for error values occurring on the acknowledge line,
- detecting a first erroneous sequence of true or false (1 to 0) on the acknowledge line while the request line remains true (1),
- detecting a second erroneous sequence of false to true (0 to 1) on the acknowledge line while the request line remains false (0), and
- putting out an error condition to a data sending unit on the bus indicating detection of one of the first erroneous sequence and the second erroneous sequence.
Dependencies are inferred from the claim text.