Apparatus for transition between network control and link control

Claim 1

In a digital communication system operating in a synchronous mode for transmitting and receiving information in a fixed byte length format wherein a message includes control data and text data in predetermined message fields, an apparatus for processing a portion of said message according to a variable byte length format comprising, in combination: a bit counter driven in sychronism with receipt of bits in said message; compare means having two sets of inputs and an output which produces a predetermined signal when matching signals are presented at said two sets of inputs, said bit counter being coupled to one of said sets of inputs and having a reset input coupled to said output; switch means for presenting a byte length code to the other of said sets of compare means inputs, said switch means being adapted to select one of a plurality of byte length codes in response to a predetermined control code contained in said message control data; and code generation means for supplying said byte length codes to said switch means, said code generation means including means for producing a code corresponding to the byte length employed in said fixed byte length format and a code corresponding to a variable byte length code contained in said message control data, whereby said compare means produces at its output an end-of-character timing pulse for use in processing said meassage data, said timing pulse having a repetition rate synchronous with fixed length bytes for processing the initial portion of said message and having a repetition rate synchronous with a different byte length dictated by said variable byte length code for processing a subsequent portion of said message.