Automatic baud rate detection

• US 5,008,902 A
• Filed: 01/25/1989
• Issued: 04/16/1991
• Est. Priority Date: 01/25/1989
• Status: Expired due to Term

• Current Assignee: ROLM Co. (Siemens AG)
• Original Assignee: International Business Machines Corporation
• Inventors: Black, David C., Key, Gary R.
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): Chin, Stephen
• Application Number:
  US07/302,172
• Time in Patent Office: 811 Days
• Field of Search: 375/10, 375/13, 375/121, 370/84, 324/78 R, 324/78 Z, 328/151, 340/825.65
• US Class Current: 375/225
• CPC Class Codes: H04L 25/0262 Arrangements for detecting the data rate of an incoming signal

Abstract

Method for determining the baud rate of a data stream by comparison of captured data to known autobaud characters. Samples are received from the communication device and stored in memory until a set of the samples are accumulated. Then, a sample clock is divided in half and the odd numbered samples are compared to a set of known autobaud characters. If a match occurs, then the sample clock is assumed to be correctly synchronized with the incoming serial data stream. If a match does not occur, then the even samples are recirculated and eight more samples are collected. The sample clock is again divided in half and the odd numbered samples are compared to the set of known autobaud characters. If a match occurs, then the sample clock is assumed to be correctly synchronized with the incoming data stream. These steps are repeated until an autobaud character match is found or an error situation is determined.

Claims

1. Method for automatically detecting transmission rate of a stream of data, comprising:

(a) sampling the data at a rate faster than the highest possible baud rate;

(b) storing the sampled data in a memory;

(c) comparing the sampled data to known data;

(d) determining if a match occurs;

(e) selecting the matched baud rate if a match occurs;

(f) recirculating a portion of the sampled data if a match does not occur; and

(g) repeating steps (a) to (f) until a match occurs.

2. Method for automatically detecting the baud rate of a stream of data as recited in claim 1, further comprising:

(a) collecting eight bits of data;

(b) collecting eight additional bits of data;

(c) comparing the sixteen bits of data to a known sixteen bits of data;

(d) recirculating eight bits of the collected data if a match does not occur; and

(e) repeating steps (b), (c), and (d) until a match occurs.

3. Method for automatically detecting the baud rate of a stream of data as recited in claim 1, further comprising error processing for detecting no possible matches.

4. Apparatus for automatically detecting the baud rate of a stream of data, comprising:

(a) means for sampling the datat at a rate faster than the highest possible baud rate;

(b) means for storing the sampled data in a memory;

(c) means for comparing the sampled data to known data;

(d) means for determining if a match occurs;

(e) means for selecting the matched baud rate if a match occurs;

(f) means for recirculating to said storing means a portion of the sampled data if a matched does not occur.

5. Apparatus for automatically detecting the baud rate of a stream of data as recited in claim 4, further comprising:

(a) means for collecting eight bits of data;

(b) means for collecting eight additional bits of data;

wherein said comparing means compares the collected sixteen bits of data to a known sixteen bits of data and said recirculating means recirculates to said storing means eight bits of the collected data if a match does not occur.

6. Apparatus for automatically detecting the baud rate of a stream of data as recited in claim 5, further comprising means for performing error processing for detecting no possible matches.