Method and apparatus for interconnection offlow-controlled communication

Abstract

A method or system or apparatus provides improved digital communication. In one aspect, flow control in performed by receiving status preprended to data units in a combined data channel, where the status data indicated the available status of a number of far end receiving channels. Thus data may be sent only to available receiving channels. In a further aspect, a frequency reference may also be transmitted by including data in data units in a combined channel. In a further aspect, an active channel can be selected among two redundant channels by use of an active bit in said data units. The invention has particular applications to ATM-type communication systems and may also be used in other communication systems.

1 - 19 . (Cancelled).  
     
     
         20 . A method for providing a timing reference over a serial data unit stream comprising: 
 determining an edge of a reference clock signal at a transmit location;    including in cells transmitted in said serial stream a timing reference field wherein said field value represents a number of bytes after a predetermined point at which a timing reference edge occurs; and    recovering at a receive location said reference clock signal from said serial stream.    
     
     
         21 . The method according to  claim 20  wherein if no occurs during a data unit, setting said timing reference field to a null value.  
     
     
         22 . The method according to  claim 20  wherein any frequency less than the data unit rate can be transmitted.  
     
     
         23 . The method according to  claim 20  wherein a recovered clock is generated one cell period later than the inserted timing.  
     
     
         24 . The method according to  claim 20  wherein a recovered clock has a resolution limited to one byte and therefore some jitter is recovered clock signal may be present.  
     
     
         25 . The method according to  claim 24  further comprising applying a local phase locked loop as said receive location to remove jitter.  
     
     
         26 . The method according to  claim 20  wherein every data unit transmitted over said link contains a timing reference portion.  
     
     
         27 - 59 . (Cancelled)