Vital digital communication system
First Claim
1. Vital digital communication system responsive to the selection of a desired command to be sent for encoding a corresponding message, transmitting and decoding the message to derive said command in a vital manner comprising:
- a transmitter including encoding means responsive to the selection of a desired command for generating and outputting said message, said message comprising a pair of multi-bit words, each word separated from other words by an identical multi-bit framing sequence, a second word of said pair complementary to a first word of said pair, the ratio of ones and zeroes in either said first or second word being constant,a receiver including vital decoding means responsive to the output of said encoder for identifying said framing bits and for identifying each word of said message, said vital decoding means including,means for sequentially producing multi-bit words in response to sequential receipt of said encoded words and means for checking that said sequentially produced multi-bit words are complementary to each other, said last-named means including,a multi-bit comparator for comparing said produced multi-bit word with a multi-bit pattern, said comparator sequentially emitting different outputs if sequential ones of said produced multi-bit words are complementary, said vital decoding means providing an output indicative of said command if, and only if, said sequentially emitted outputs are provided.
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Accused Products
Abstract
An all-digital communication system is arranged to exhibit fail-safe qualities. Each message includes a pair of words, each word separated from every other word by framing information in the form of two bits, either 1/0 or 0/1. Each word in the message is arranged to exhibit a constant ratio of 1'"'"'s to 0'"'"'s, so that more than a single change in any bit location is needed to change from one valid message word to another. The second word in each message is the complement of the first. Two decoders are disclosed, a hard-wired embodiment and an embodiment employing a microprocessor. In the hard-wired embodiment, straightforward decoding is employed to determine the apparent message, and the apparent message is encoded to generate a locally generated message which is then compared, bit by bit, with the received message employing vital logic techniques. Assuming each of the received and locally generated bits compare, the message is validated.
In the microprocessor embodiment, decoding of each word is accomplished by a table. Several checks are run to determine that the microprocessor is operating properly. The checks if successfully completed, produce a check word, which is not stored in the machine. The check word generated by decoding of the second word of a message should be complement of the first check word. External hardware determines the existence of each check word, in sequence, and allows the decoded microprocessor output to be effective.
20 Citations
18 Claims
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1. Vital digital communication system responsive to the selection of a desired command to be sent for encoding a corresponding message, transmitting and decoding the message to derive said command in a vital manner comprising:
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a transmitter including encoding means responsive to the selection of a desired command for generating and outputting said message, said message comprising a pair of multi-bit words, each word separated from other words by an identical multi-bit framing sequence, a second word of said pair complementary to a first word of said pair, the ratio of ones and zeroes in either said first or second word being constant, a receiver including vital decoding means responsive to the output of said encoder for identifying said framing bits and for identifying each word of said message, said vital decoding means including, means for sequentially producing multi-bit words in response to sequential receipt of said encoded words and means for checking that said sequentially produced multi-bit words are complementary to each other, said last-named means including, a multi-bit comparator for comparing said produced multi-bit word with a multi-bit pattern, said comparator sequentially emitting different outputs if sequential ones of said produced multi-bit words are complementary, said vital decoding means providing an output indicative of said command if, and only if, said sequentially emitted outputs are provided. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A vital decoder for a digital communication system in which one multi-bit message of a plurality of messages is repetitively transmitted in serial form, said multi-bit message including two words, a second complementary to a first, each word having a constant ratio of 1'"'"'s to 0'"'"'s and words separated by an identical multi-bit framing pattern, said decoder comprising:
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register means into which a received message is clocked, bit by bit, frame detector means coupled to said register means, a storage register also coupled to said register means and controlled by said frame detector means for storage of a message word, apparent message determining means responsive to said storage register and coupled to output means, for generating an apparent message, encoding means responsive to said apparent message determining means for generating a locally encoded message corresponding to said apparent message, and vital logic means responsive to both said storage register and to said apparent message for enabling said output means, said vital logic means including a multi-bit comparator comparing received words from said storage register and corresponding words from said encoding means and producing two distinctive sequential outputs if said words are identical, said vital logic means enabling said output means if, and only if, said multi-bit comparator produces said two distinctive outputs, alternately and in sequence. - View Dependent Claims (13, 14)
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15. A vital decoder for a digital message which digital message includes a pair of multi-bit words separated from other words by a predetermined multi-bit framing sequence, a second word of said message complementary to a first word, said decoder including a single central processing means, said central processing means including:
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means responsive to said framing sequence for identifying each multi-bit word; means responsive to each said multi-bit word for determining a command represented thereby; checking means for checking control of said central processing means over its own output ports, said checking means producing one of two distinctive multi-bit words in response to completion of said checking after receipt of each said message word, said distinctive multi-bit words being complementary if said message words are valid and said checks are favorable, said decoder further including; logic means responsive to said distinctive multi-bit words for validating operation of said central processing means, said logic means including a multi-bit comparator for comparing said distinctive words to predetermined bit patterns and validating said operation if, and only if, said distinctive words are produced alternately and in sequence, and means responsive to validation by said logic means for enabling utilization of a command provided by said central processing means. - View Dependent Claims (16, 17, 18)
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Specification