Single parity bit generation circuit

• US 4,538,271 A
• Filed: 05/04/1983
• Issued: 08/27/1985
• Est. Priority Date: 05/04/1983
• Status: Expired due to Term

• Current Assignee: American Bell Incorporated
• Original Assignee: AT&T Information Systems Inc. (AT&T, Inc.)
• Inventors: Kohs, Dwight W.
• Primary Examiner(s): Smith, Jerry
• Assistant Examiner(s): Ungerman, Mark
• Application Number:
  US06/491,279
• Time in Patent Office: 846 Days
• Field of Search: 371/49, 371/50, 371/51, 365/200, 365/201, 364/738
• US Class Current: 714/801
• CPC Class Codes: G06F 11/10 Adding special bits or symbols to the coded information, e.g. parity check, casting out 9's or 11's

Abstract

The subject parity circuit generates a single parity bit for a prescribed DATA SET. The DATA SET comprises n bytes which are simultaneously transmitted to the parity circuit over n data transmission leads. The n bytes are simultaneously combined bit by bit to determine whether an odd or even number of bits have been received. A cummulative sum is determined, and the single parity bit is generated with the receipt of the last n bits of the DATA SET.

Claims

1. A method for generating a single parity bit for a prescribed set of data where each set comprises n serially transmitted increments of data with each of said increments containing a plurality of bits, which bits are simultaneously input to a parity circuit over a like plurality of data transmission leads in synchronization with control signals which delimit the beginning and the end of said prescribed set wherein said method includes the steps of:

combining simultaneously in response to a first control signal that delimits the beginning of said prescribed set all of said bits in each one of said increments as received to produce an associated representative bit for each of the first received n-1 increments of said n increments indicating whether an odd or even number of 1 bits are included in each of said n-1 increments;

registering sequentially the odd or even state of each of said produced represented bits for each of said received n-1 increments;

producing from said registered representative bits an indicative bit indicating a cumulative odd or even state of all received n-1 increments in response to a second control signal that delimits the end of said prescribed set corresponding to a receipt of a last increment, "n"; and

generating in response to the receipt of said "n" increment and said indicative bit a single parity bit indicative of the parity for said prescribed set of data.

2. The method of claim 1 wherein the step of registering sequentially includes:

initializing said parity circuit to indicate a receipt of a first increment of said prescribed set of data in response to a first prepared representative bit.

3. The method of claim 1 wherein the step of producing includes:

storing a cumulative indication of an odd or even number of 1 representative bits produced in response to each of said received n-1 increments.

4. The method of claim 1 wherein the step of producing further includes:

inserting said indicative bit into a predetermined last bit position of said received "n" increment of said prescribed set of data.

5. The method of claim 1 wherein the step of generating includes:

combining said "n" increment and said indicative bit to produce a single parity bit for said prescribed set of data.

6. In a data handling system, a parity circuit connected to a plurality of data transmission leads over which is transmitted a prescribed data set having n increments of data where each of said increments contains a like plurality of bits and where each of said increments included in said data set is serially transmitted to said parity circuit in synchronization with control signals that delimit the first and last increment of said prescribed data set, comprising:

means connected to said data transmission leads for simultaneously combining in response to a first control signal that delimits the first increment of said prescribed data set all of said bits in each one of said increments as received to produce an associated representative bit for each of the first received n-1 increments indicative of the odd or even number of 1 bits included in each received n-1 increment;

sequential bit evaluator means connected to said simultaneously combining means and responsive to said produced representative bits associated with said n-1 increments and further responsive to a second control signal that delimits the end of said prescribed data set as generated with a receipt of a last increment n for generating an indicative bit representing the odd or even cumulative number of 1 bits included in all received n-1 increments; and

means connected to said sequential bit evaluator means and responsive to said indicative bit and the receipt of said n increment for generating a single parity bit indicative of the parity for said prescribed data set.

7. The circuit of claim 6 wherein said sequential bit evaluator means comprises:

means for initializing said parity circuit to indicate a receipt of a first associated representative bit of a first increment of said prescribed data set.

8. The circuit of claim 7 wherein said sequential bit evaluator means further comprises:

means for registering sequentially an indication of the even or odd state of each of said produced representative bits for each of said received n-1 increments; and

means responsive to said registering means for providing a bit indicative of the odd or even number of 1 bits included in each received n-1 increment of said prescribed data set.

9. The circuit of claim 8 wherein said sequential bit evaluator means further comprises:

means for inserting said indicative bit into a preselected bit position of said received n increment of data in said prescribed data set.

10. The circuit of claim 6 wherein said generating means comprises:

means for combining in response to a receipt of said n increment over said data transmission leads and said indicative bit into said single parity bit for said prescribed data set.