Chips and Technologies, Llc.

James A Picard

Morris E Jones, Jr

A system for performing input and output operations to and from a processor in which interrupts for I/O operations are conditionally generated internally rather than externally by (Super State.TM.) microcode residing in a separate address space in memory in an area protected from the user. A (superblock) register in the processor points to the Super State area in memory. If the Super State mode is turned on, an interrupt is generated within the processor whenever the control table allows. The interrupt directs the processor to the register and hence to the Super State code. By way of example, the Super State code controls power and access to the port, decides whether to put the interrupt in memory and emulate the I/O, and counts access to the port. The invention provides a processor with the flexibility of performing I/O operations to and from memory and/or to a peripheral or to trap an interrupt into a new operating environment for device emulation. Device emulation and monitoring is allowed without considerable program overhead. The invention provides a powerful, efficient I/O control system which can change or adapt in response the changing demands of an application program.

System for performing input and output operations to and from a processor

An efficient organization for microcoded instruction sets which have processor operations in which not all the bits of an instruction word are required. The organization has two registers for receiving and holding the first and second byte of instructions at a time, a first ROM connected to the register for decoding the first byte into control signals for operation of said microprocessor. One of these control signals is generated whenever the portion of the second instruction byte is required. The organization also has a second ROM connected to the register for decoding the portion of the second byte into control signals. Connected to said first and second ROMs is a multiplexer which selects the decoded second byte control signals for operation of the microprocessor responsive to the first ROM control signal. The combined size of the first and second ROMs is much smaller compared to that of a ROM which decodes both bytes all the time and achieves a great savings in the space occupied by the processor integrated circuit.

Two-ROM multibyte microcode address selection method and apparatus

An arithmetic logic unit for a microprocessor is shown and described for use in a 24-bit data path where the ALU includes three separate ALU portions, one for each byte of the data path, and three separate control signals, one for each portion of the ALU. The ALU provides a variety of arithmetic and logic functions for application to 24-bit operands, but also includes a capability of manipulating such operands in accordance with sign extended opcodes without actually physically executing a sign extend operation within the microprocessor. In this manner, the ALU executes the necessary logic functions to provide the same ultimate result as sign bit extension, but does not require a separate sign bit extension step within the microprocessor to convert signed byte operand into a signed word operand.

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San Jose, CA, United States of America

James A Picard