An access unit for a shared memory for use in a microprogrammable processor is provided utilizing a multiplexing scheme. Two functionally different inputs, one for data, the other for microinstructions are exclusively gated to memory in synchronization with microprogram control timing cycles to permit accessing the memory at separate times via a single channel.

A serial buss processor with detailed description of program branching and register addressing. A mask and branch instruction is utilized to effect a relative program branch of up to N + 1 address locations away from the address of the current or masking branch instruction, where N is the number of bits in the data operand. Register addressing is partly direct and partly indirect. The indirect register address scheme employs a directly addressable register, the contents of which are interpreted ...

A bit addressable, variable field memory system partitioned into a plurality of individually addressable memory stacks and employing time-shared accessing circuitry in conjunction with the use of serial, multi-phase accessing of the memory stacks, whereby the advantages of serial memory stack accessing are achieved without significantly increasing the overall memory accessing time over that obtained for parallel accessing.

A data processing system is disclosed in which a high-speed processor is added to a slow-speed processor and in which both processors have access to a first memory unit with the slow processor having access priority over the fast processor. In order to allow the fast processor to operate without losing data when a conflict occurs during a write operation, a second memory is coupled to the fast processor in which is stored all the data stored in the first memory. When the fast processor attempts ...

A memory access selection circuit including a microprocessor, address, data and control multiplexers, a random access memory, storage circuits and related logic circuitry. This circuit allows both an external processor and the microprocessor to receive data from and transmit data to, the random access memory. The microprocessor controls access of the external processor to the random access memory by controlling and monitoring the multiplexer and storage circuits. This prevents erroneous data, ad...

An improved multiword data register array which features RAM technology to provide a greater memory capacity in a smaller space than a conventional register arrays. Whereas RAM technology does not ordinarily include the capability of simultaneously reading and writing, in accordance with the present invention, data may be written into the register on a first half cycle of a clock signal and read out of memory on the second half cycle of the same clock signal. If the writing and the reading of th...

An address computation system for updating starting addresses of data arrays in an array processor within an instruction cycle. A first set of registers is provided for storing starting addresses for each array. A second set of registers is provided for storing current addresses for each array. Logic is provided for initially providing, at the beginning of a series of computation steps to be executed repetitively, an address from a register in the first set of registers, changing that address, a...

A single chip cache address comparator with an on-chip static RAM for storing and checking the cache tags of an external cache memory. This cache address comparator has a built-in incrementing counter which controls the burst fill of the internal cache of a 68020/68030 microprocessor from the associated external cache memory within the required five processor clock cycles. Further, additional on-chip control logic is provided to control the 68020/68030 system buses to coordinate a burst fill ope...

A microcomputer includes I/O ports and registers which are mapped in memory space along with RAM and ROM and in which hardware invisible to the programmer performs a bus arbitration sequence to acquire an external bus when an off-chip reference requires the bus; and in which memory space that is used for on-chip references is recovered for use in external memory by manipulating bits in the memory address.

When a CPU accesses a memory device, the upper address data of an address signal is transmitted as parallel signals while the upper address data thereof is transmitted as serial signals after parallel-serial conversion. In order to convert the upper address into the serial signals, a parallel-serial converter is disposed on the side of the CPU or on the side of the CPU of an address bus while a serial-parallel converter is disposed on the side of a memory device or on the side of the memory devi...