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CHARACTER SYNCHRONIZATION METHOD

IP.com Disclosure Number: IPCOM000060882D
Original Publication Date: 1986-May-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 46K

Publishing Venue

IBM

Related People

Skarshinski, L: AUTHOR

Abstract

A problem in implementing a serial protocol with run-length-limited code is to reliably determine when character synchronization is lost, and when it is reacquired. This is because the high-speed logic, if allowed, will reset the character clock every time that a predetermined character is encountered, potentially slivering character clocks and producing unexpected results in low speed logic. A loss of character synchronization poses a problem only when a frame is being received and processed by a port; this loss of sync at the beginning of a long frame will not be noticed until a frame trailer or an idle sequence is encountered. The proposed method uses code violation statics to recognize when the character clock is aligned with the incoming characters.

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CHARACTER SYNCHRONIZATION METHOD

A problem in implementing a serial protocol with run-length-limited code is to reliably determine when character synchronization is lost, and when it is reacquired. This is because the high-speed logic, if allowed, will reset the character clock every time that a predetermined character is encountered, potentially slivering character clocks and producing unexpected results in low speed logic. A loss of character synchronization poses a problem only when a frame is being received and processed by a port; this loss of sync at the beginning of a long frame will not be noticed until a frame trailer or an idle sequence is encountered. The proposed method uses code violation statics to recognize when the character clock is aligned with the incoming characters. Misalignment of the character clock and the data will produce code violations with a probability p(cv). An examination of a few characters shows that this probability is about 0.5 for a string of data and is close to 1.0 for an idle string. The method discussed will work well with a long string of data and, therefore, will also work for any other string in a selected code. CHARACTER SYNCHRONIZATION METHOD Given N and M counters, the N counter would count up to Ncharacter clock cycles when started by a code violation. If no additional code violations are detected during this time, the M counter would be incremented; if a code violation is encountered, the N counter is reset and the M counter is decremented. (The M counter cannot increment through all '1' state and cannot decrement through the all '0' state.) The state of the M counter would indicate in or out of character...