Logically transportable microprocessor interface control unit permitting bus transfers with different but compatible other microprocessors
First Claim
1. A single-chip microprocessor comprising:
- external signal pins to which off-chip devices are connected;
a microprocessing unit; and
an interface control unit, said interface control unit being connected to said microprocessing unit and to said external signal pins of said single-chip microprocessor, said microprocessing unit and said interface control unit being logically distinct elements, such that said interface control unit is logically transportable for use with other and different microprocessing units;
said interface control unit comprising;
execution means connected to said microprocessing unit and to said external signal pins; and
control means for controlling said execution means and for performing signal sequencing at said external signal pins, said signal sequencing being called a bus cycle, said control means being responsive to commands from said microprocessing unit and to control signals from said off-chip devices;
said control means including command means responsive to said commands from said microprocessing unit and status means for presenting status to said microprocessing unit describing the outcome of each command, wherein said command means causes said execution means to perform a data transfer in response to a command from said microprocessing unit, and said status means presents the outcome status of said particular command upon logical completion of said data transfer.
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Abstract
A transportable bus control architecture for single-chip microprocessors consists of an interface control unit that is logically independent of the associated co-resident, common clock-driven microprocessing unit. This independence allows the interface control unit logic to be used with a variety of microprocessing units. The interface control unit presents an external appearance that is compatible with the peripheral devices of a specific microprocessor referred to as the "compatible microprocessor", thereby making available to an associated co-resident microprocessing unit the support devices of the compatible microprocessor. The interface control unit can also access other external devices not related and transparent to the devices of the compatible microprocessor. The interface control unit is logically divided into an execution section and a control section. The execution section is controlled by the control section and comprises various registers, latches, multiplexers, logic, and data and address paths that provide communication between the co-resident microprocessing unit and off-chip devices. The control section of the interface control unit executes commands from the co-resident microprocessing unit and also performs bus arbitration, interrupt, and external reset functions. Bus cycles are memory-access or service, depending on the command from the co-resident microprocessing unit. Service cycles perform the interrupt acknowledge functions and other sense and control functions requested by the co-resident microprocessing unit. These sense and control functions have the special feature of being pin-programmable and pin-readable by the microprocessing unit. All action initiated by commands from the microprocessing unit elicits a comprehensive status response from the interface control unit.
95 Citations
24 Claims
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1. A single-chip microprocessor comprising:
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external signal pins to which off-chip devices are connected; a microprocessing unit; and an interface control unit, said interface control unit being connected to said microprocessing unit and to said external signal pins of said single-chip microprocessor, said microprocessing unit and said interface control unit being logically distinct elements, such that said interface control unit is logically transportable for use with other and different microprocessing units; said interface control unit comprising; execution means connected to said microprocessing unit and to said external signal pins; and control means for controlling said execution means and for performing signal sequencing at said external signal pins, said signal sequencing being called a bus cycle, said control means being responsive to commands from said microprocessing unit and to control signals from said off-chip devices; said control means including command means responsive to said commands from said microprocessing unit and status means for presenting status to said microprocessing unit describing the outcome of each command, wherein said command means causes said execution means to perform a data transfer in response to a command from said microprocessing unit, and said status means presents the outcome status of said particular command upon logical completion of said data transfer. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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- 12. bus grant enable means responsive to said bus arbitration means for enabling and disabling said granting of said bus.
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13. A bus control architecture for microprocessors consisting of a logically independent interface control unit capable of being used with a variety of microprocessing units, said interface control unit permitting a microprocessing unit to be used with externally connected support devices of another, different microprocessor, said interface control unit being connected to memory means for storing data, said memory means being divided into memory address space and service address space, said interface control unit comprising:
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address means for providing an output address unit and said externally connected support devices during a bus cycle; data means for providing a bidirectional data path between said microprocessing unit and said externally connected support devices during a bus cycle; processor command means for receiving and buffering commands from said microprocessing unit to said interface control unit; and control means connected to said processor command means and responsive to commands from said microprocessing unit for performing either a memory access bus cycle or a service access bus cycle depending on the command from said microprocessing unit wherein memory address space is accessed during a memory access bus cycle and service cycle address space is addressed during a service bus cycle, said service bus cycle address space being divided into interrupt-acknowledge address space for space externally connected support devices and control and sense address space of said microprocessing unit to permit an extension of the functional capability of said microprocessing unit in a manner that is transparent to said externally connected support devices of said compatible microprocessor. - View Dependent Claims (15, 17, 18, 19, 20, 21, 22, 23, 24)
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Specification