Block mode digital signal conditioning method and apparatus
First Claim
1. A method of conditioning a digital data string for transmission between a first and a second digital unit on an asynchronous communication line, the method comprising the steps of:
- a. determining a maximum number of bits per byte each of the first and second digital units can accept;
b. serializing a plurality of data bytes to be transmitted from the first digital unit into a continuous string of data bits;
c. prefixing a preselected header string to the data string to identify the transmission source;
d. packing the serialized data string of step b. into pseudo-bytes each having a number of bits that is no longer than the smaller of the maximum numbers determined in step a.;
e. appending a preselected control character string following the data string to identify the end of the packed data string; and
f. arithmetically adding an offset value to each pseudo-byte, the value of which is dependent on and preselected for the length of the pseudo-bytes.
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Accused Products
Abstract
Block mode is a method of formatting data when sending it to and from the host computer. Some host computer operating systems make it difficult for the user'"'"'s program to send or receive the full ASCII character set. The block mode protocol lets you send and receive messages which use the full ASCII character set (including lowercase characters and control characters), even though your host computer'"'"'s operating system makes it difficult to send and receive certain ASCII characters. (Indeed, even full eight-bit binary data bytes may be sent to or from the terminal in block mode.) This is accomplished by means of a packing scheme, in which messages using the full character set are packed into character strings using a subset of that character set.
Also, the block mode protocol provides error detection and automatic retransmission of bad data blocks. This lets you transfer data to and from the terminal, without errors, despite occasional noise on the communications line. Block mode is completely independent of whether or not prompt mode is used and of whether the terminal is using full duplex or half duplex communications.
When in block mode, data is packed into blocks and transmitted as a unit. Each block contains an "even/odd" counter (block control byte one, bit one) which is used in an "ACK/NAK" protocol. This protocol lets the host and terminal inform each other when a block has been received incorrectly. (The block received incorrectly is then retransmitted.)
31 Citations
6 Claims
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1. A method of conditioning a digital data string for transmission between a first and a second digital unit on an asynchronous communication line, the method comprising the steps of:
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a. determining a maximum number of bits per byte each of the first and second digital units can accept; b. serializing a plurality of data bytes to be transmitted from the first digital unit into a continuous string of data bits; c. prefixing a preselected header string to the data string to identify the transmission source; d. packing the serialized data string of step b. into pseudo-bytes each having a number of bits that is no longer than the smaller of the maximum numbers determined in step a.; e. appending a preselected control character string following the data string to identify the end of the packed data string; and f. arithmetically adding an offset value to each pseudo-byte, the value of which is dependent on and preselected for the length of the pseudo-bytes. - View Dependent Claims (2, 3)
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4. Digital signal conditioning apparatus for conditioning a data string to be transmitted between a first and a second digital unit on an asynchronous communications line wherein the maximum number of bits per data byte that the first and second digital units can recognize is unequal, said apparatus comprising:
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first means for serializing the data bytes to be transmitted from the first digital unit into a continuous string of data bits; second means for prefixing a preselected header string to the serialized data string of the first means to identify the transmission source; third means for packing the serialized data string from the first means into pseudo-bytes each having a number of bits that is equal to the smaller of the maximum number of bits per byte that the first and second digital units can recognize, the third means including means for arithmetically adding an offset value to each pseudo-byte in the packed data string forming modified pseudo-bytes, the value of which is dependent on and preselected for the length of the pseudo-bytes; and fourth means for appending a preselected control character string following the data string to identify the end of the packed data string. - View Dependent Claims (5, 6)
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Specification