Abstract: A method and apparatus for the elimination of any net d.c. component from the transmission of binary sequential data in a run length limited code where the encoding set has less than the number of code values required to provide one-to-one mapping from source data to an encoded set satisfying preselected constraints. The past and current parity and charge of the encoded words are employed as parameters in the method to determine encoding schemes satisfying criteria such as run length limit.

Abstract: A loop system couples a CPU channel to bulk storage devices via a loop controller and device adapter. The loop system is characterized by equal fixed-length, multi-byte frames, each frame of which being assignable to only one terminal at a time. The system is further characterized by having a fixed loop delay greatly exceeding the frame duration by virtue of the high data rate.Dynamically variable frame assignment occurs when the primary terminal generates an unassigned empty frame in response to each assigned full (read) frame from a secondary terminal. The primary further generates an assigned full (write) frame upon receipt of each service (write) request frame from a secondary terminal. Lastly, the primary can send access command frames for each received unassigned empty frame or any other frame that does not imply a demand for bandwidth by the secondary.

Abstract: A method and apparatus for synchronizing frame delimited bit stream messages on a high speed loop for communication among storage system elements. The method especially minimizes the time for attaining frame and byte synchronization among terminals attaching storage elements to the loop. The method comprises the steps of (1) synchronizing terminals downstream from a faulty terminal to a first synch reference as generated by the faulty terminal and further (2) synching the terminals upstream therefrom to a second synch pattern generated by the primary terminal responsive to the first reference. As a consequence, the system resynchs as a function of resynching of the faulty station alone. Transmission efficiency is improved by logically assigning for loop attachment only those loop secondary terminals whose storage elements have an aggregate bandwidth less than the available instantaneous loop bandwidth. Further improvement is obtained by dynamically varying the frame assignments.

Abstract: An improved clock retiming system for pulse coded data is provided in which the clock signals are extracted from the encoded data and first and second signals of the same amplitude and frequency but of different phase are generated from the clock signals. First and second amplifiers having variable gains provide amplification for the first and second signals, respectively. The first and second amplified signals are summed to produce a third signal having a phase which is a function of the relative amplitudes of the first and second amplified signals. The original pulse encoded data is sampled with the third signal to produce the retimed data output. The original pulse encoded data is also utilized to sample the third signal. The resulting signal is filtered to provide a DC voltage feedback error signal indicative of the phase difference between the third signal and the original pulse encoded data.

Abstract: A method and means for modifying up to k bits in each byte of (n+k) bits to be accessed with respect to counterpart minor loops of a sequentially accessed byte-organized major/minor loop memory array. The combination of bad byte location pointers and a byte mask is used to delete bits on bad bytes extracted from the memory or to insert zeroes into defective loop locations when bad bytes are written into the memory. Alternatively, the ith bit in each byte of (n+1) bits to be accessed may be modified through the utilization of the value of the ith bit written into the byte position of n+1st bit, while the ith bit of a defective byte position is zeroed. As a bad byte is extracted, the value of the n+1st bit is substituted for the ith bit. A dense list, rather than a sparse bad byte pointer list, is used.