Digital Equipment Corporation

Digital Equipment International Limited

Robert J Galuszka

Neal Andrew Crook

Andrew J Walton

Paul L Bruce

Stewart F Bryant

Clinton Choi

John M Lenthall

Bipin Mistry

Vincent G Gavin

A high performance data link interface includes receive and transmit data framing paths. The data link interface interlocks certain communication link control signals, such as the CCITT standard data set signals, with data being received or transmitted through the interface to correlate a transmission error directly to a particular data transmission for rapid and efficient error recovery.

High speed transmission line interface

An apparatus and method for supplying an address and data to an external memory device. The number of pins available for supplying the address is less than the number of address lines required at the external memory device. A register is used to store the high order bits of the address and is pre-loaded with a default page value. An output of the register is coupled to an address input of the external memory. If the high order bits of the address are equal to the default page value, a control device couples the data lines directly to the external memory device and a read or write operation follows. If the two values are different, a paging cycle is performed where the high order address bits are latched through the register to the address input of the external memory and then the data bits are coupled to the external memory device. If the default page value points to the most accessed portion of the external memory device, no paging is performed during access to that portion of the external memory and processing time is saved when reads or writes of data are made to that portion of the external memory.

Paged memory scheme

A method and apparatus for improving the performance of the transferring of transaction handshakes between sections of synchronous logic which are in different timing domains providing immunity from set-up and hold violations and associated problems of metastability, by reducing the time overhead required for signal synchronization.

Handshake synchronization system

In an apparatus including a first and second processor coupled to a shared bit-RAM memory, simultaneous write operations can be performed without internal race conditions in the memory. Rather than using arbitration, a write is generated by logic in each processor only when data to be written is different from data currently stored in a given location. A processor can write data to the bit-RAM only when a write pulse has been generated by that processor. Clocking signals from the processors are used to insure that a read and a write operation are not performed by two separate processors.

Apparatus for simultaneous write access to a single bit memory

A bus interface coupling one or more processors to a standardized bus, such as the Futurebus. The bus interface controls the assertion of all address and data handshaking signals on the bus while sending control signals to address/data transceivers coupled in between the bus and the processors. The interface comprises a plurality of synchronous state machines coupled to the processors for passing status and command data to a plurality of master and slave devices coupled to the bus. The interface also comprises a plurality of asynchronous state machines coupled between the synchronous state machines and the bus. The asynchronous machines quickly detect and assert the necessary handshaking signals of the bus protocol. The interface also controls the address/data transceivers coupled between the processors and the bus and provides an efficient throughput of data to and from the bus. Items coupled to the bus interface can operate either as slave or master devices. The bus interface handles the complex asynchronous interface with the bus and provides a much easier synchronous interface with the master and slave devices coupled to the bus.

Growing community of inventors

Reading, United Kingdom

Robert J Galuszka