Method of link word synchronization
A method for word synchronization can be applied to asynchronous devices including SERDES devices connected across serial lines. A state transition methodology characterizes the state of the device based on control characters received consistently across the serial lines and channels the system to a state of word synchronization. Loss of synchronization and transmission errors lead to a re-establishment of synchronization.
1. A method for transmitting digital words of a specific bit length between a first and a second digital device, comprising the steps of:
(a) dividing the digital words into two or more word portions of equal bit length, the number of portions being an exponential power of 2;
(b) transmitting each word portion from a serializer at one device to a deserializer at the other device on a separate serial line dedicated to each portion, the serial lines operating in parallel;
(c) enabling synchronized receipt of the portions of digital words by the deserializers at the second digital device by transmitting by the serializers of the first device an enabling idle sequence including a first control word simultaneously on each of the serial lines, to the serializers at the second digital device, the second device then entering a half-sync mode;
(d) after entering the half-sync mode at the second digital device, transmitting from the serializers at the second digital device to the deserializers at the first digital device an enabling idle sequence including a second control word, receipt of the idle sequence and second control word enabling the first digital device to receive word portions synchronously; and
(e) transmitting packet data in an active state between the two digital devices.
2. The method of claim 1 wherein at least one control word is transmitted simultaneously on each serial line with or between each data packet transmitted in either direction between the two digital devices.
3. The method of claim 2 wherein a control word detected by deserializers at either digital device is inconsistent across the deserializers, and the deserializers as a result repeat the synchronization sequence before returning to active transmission of packet data.