Abstract: The present invention provides writing compositions that are capable of being erased or changed in color chemically. The present invention also provides erasing media for erasing or changing the color of marks produced with the writing compositions, as well as writing systems and incorporating the erasing media and the writing compositions. The present invention further provides writing instruments produced using the writing compositions.

Abstract: A system for communicating data between a main processor and a peripheral processor over a fiber optic interface. The interface is a dedicated, point-to-point link operating in full-duplex, asynchronous mode. Dual fibers and physical layer controllers are used in a cascaded fashion to double the throughput of the interface. Frame control logic coordinates formatting of data into frames for transmission over the interface. Frame format and interface protocol are based on FDDI, but are improved to more efficiently transfer data in a point-to-point implementation. Frame Check Sequences are generated and verified to ensure error-free data transfers. Frame sending and frame receiving logic communicate with the main and peripheral processors, accepting data transfer requests and forwarding received data.

Abstract: A memory system which is shared by a plurality of requestors each of which supply read and write address bits to the memory system is read out of, or written into, in accordance with read and write address bits. A sequencer is utilized to initiate a sequence of timing signals that control the reading, writing and partial writing of data. Certain ones of these signals occur at fixed intervals from the receipt of an initial load address signal. A read address circuit coupled to receive the read address bits generates a set of check bits. A read address stack means stores each set of read address check bits upon the occurrence of an associated load read address stack signal. A write address check bit generator means is coupled to receive write address bits and to generate a set of check bits representative of the write address bits. A write address stack means stores each set of the write address check bits upon the occurrence of an associated load write address stack signal.

Abstract: An error correcting check of a memory system is provided when a memory in which the Dynamic Random Access Memory (DRAM) is of the type which has input lines that are directly coupled to its output lines. Utilizing this type of DRAM, the memory system employs controls, input, output and read circuitry to read bits out of the memory via the output circuitry and write circuitry to write bits into the memory via the input circuitry. An error checking and correction circuit is coupled to the output means which includes a check bit generator and a syndrome generator, and a control means energizes the error checking and correcting means during the write cycle, as well as the read cycle, so that the errors are detected during the write cycle as well as the read cycle. In this manner, errors which occur in circuitry other than the memory, which includes the memory driving and reading logic and also the check bit generator logic translators and syndrome generators, may be separately detected from memory errors.

Abstract: A failure detection system for variable field partial write system for merging data bits in a memory word upon programmable request is described. The variable bit field can be selected for any number of bit positions from a single bit up to and including a full data word, where data words are comprised of a predetermined number of bytes each containing a predetermined number of bits. A Start Bit Code defines the location of the start of the bit field to be written and an End Bit Code defines the bit after the last bit that is to be merged and written. Write and Read Data to be used in the partial merge operation are stored in a Merge Register along with a code derived from the Start and End Code bits. The bits not used are stored in a Non-Merge Register. Parities are compared to verify that a parity error did not occur when the Merge Register was loaded.