Abstract: A microprocessor on a monolithic integrated circuit is provided having a single clock input pin for receiving a clock input signal. The clock input signal is used to gate address data onto the address bus and to enable a data input dynamic latch. In addition the input clock signal is used to generate two complementary non-overlapping clock signals used for synchronizing purposes within the microprocessor.

Abstract: A digital data processor on a single monolithic integrated circuit chip is provided which uses one less pin. The elimination of the pin is accomplished by using, internally to the processor, a valid memory address signal to gate information from the address but to an address output line. Whenever an address is not present on the address bus all logic "1's" are generated on the address output bus.

Abstract: A microprocessor comprises an internal address bus having a first portion (2,4) having a plurality of conductors carrying the low order address byte and a second portion (10) having a plurality of conductors for carrying the high order address byte. The microprocessor further comprises a plurality of registers, including an incrementor (12,13), a program counter (14,15), a temporary register (16,17), a stack pointer (18,19), an index register (20,21), and an accumulator (22,24), each comprising a pair of 8-bit registers for temporarily storing information. An arithmetic logic unit (28) performs computational operations on digital information within the microprocessor. The microprocessor includes a pair of internal data buses (6,8) each having a plurality of conductors for conducting digital information within the microprocessor. Means are provided for coupling selected ones of the registers, or the high or low order portions thereof, to the first and second data buses.

Abstract: A digital system including a plurality of metal-oxide-semiconductor (MOS) chip random access memories (RAM), read only memories (ROM) and peripheral interface adaptors coupled to a common bidirectional data bus which is coupled to and controlled by a microprocessor unit (MPU). Each peripheral interface adaptor includes a control register loadable under program control. The contents of the control register control selection of several registers within the interface adaptor. The control register also controls other functions of the peripheral interface adaptor, including determining direction of data movement at the peripheral buffers of the interface adaptor. The contents of the control register of each interface adaptor are monitorable by the microprocessor unit.

Abstract: A peripheral interface adaptor (PIA) circuit for data processing systems contains memory elements or control registers allowing modification under program control of the logical functions of the PIA.The peripheral interface adaptor includes a plurality of system data bus buffer circuits coupled to a system data bus and further includes peripheral interface buffer circuits coupled to a bidirectional peripheral data bus. The direction of data flow in the peripheral data bus is controlled by a data direction register. Data from the system data bus buffer is entered into an input register, and is transferred from there to an input bus coupled to the control register, a data direction register and a data register. Data from the peripheral data bus, the data direction register and the control register are transferred via an output bus to the system data bus buffers.

Abstract: A circuit and a method for adding an 8-bit operand to a 16-bit operand are disclosed such that the number of machine cycles required by a data processor to perform such an addition is reduced. The 8-bit operand and the least significant byte of the 16-bit operand are added together within an 8-bit adder circuit to generate the least significant byte of the result. Simultaneously, the most significant byte of the 16-bit operand is stored in a temporary register and is also input to an increment/decrement network. The adder circuit, after a given delay time, generates a carry signal depending on whether a carry-out was produced by the addition. The carry signal and the sign bit of the 8-bit operand control the mode of operation of the increment/decrement network and determine whether the increment/decrement network or the temporary register will be selected to provide the most significant byte of the result.

Abstract: An N-channel field effect transistor microprocessor includes an arithmetic logic unit, a plurality of working registers and address generating circuitry coupled to an internal bus. Control circuitry is coupled to the arithmetic logic unit, the working registers, and the address generating circuitry for producing control signals for controlling operation of the arithmetic logic unit, the working registers, and the address generating circuitry. The microprocessor requires only a single external power supply, and includes means connected to the external power supply for providing electrical energy to the working registers, the arithmetic logic unit, the control circuitry, and the address generating circuitry in order to effect operation thereof.

Abstract: A digital system includes a microprocessor coupled to a data bus and an address bus. A memory for storing data and instructions is connected to the data bus and the address bus. A peripheral device is connected to an interface adaptor. The interface adaptor is connected to the data bus and the address bus, and performs the function of interfacing between the digital system and a peripheral device, such as a printer or a display device. The microprocessor includes logic circuitry for generating a Valid Memory Address (VMA) output. The VMA output is used to generate an enable signal applied to the memory and the adaptor to enable the memory and the adaptor to be accessed by the microprocessor when the binary address on the address bus is valid and to prevent the memory and the adaptor from being accessed by the microprocessor when the binary address on the address bus is not valid with respect to the microprocessor.

Abstract: A microprocessor system includes a microprocessor, a memory, and an interface adaptor all coupled to a data bus. The interface adaptor is coupled between the data bus and a peripheral device, such as a teleprinter. A first interrupt conductor is connected to the peripheral device and to interrupt logic circuitry in the interface adaptor. A second interrupt conductor is connected to the microprocessor and the interrupt logic circuitry. The interrupt logic circuitry is also coupled to and interrogatable by the microprocessor via the data bus. The interrupt logic circuitry stores interrupt contrl information from the data bus, and generates a second interrupt signal on the second interrupt conductor in response to the stored interrupt control information and an interrupt signal generated on the first interrupt conductor by the peripheral device.

Abstract: A digital system comprises a plurality of metal-oxide-semiconductors (MOS) chip random access memory (RAM) and read only memory (ROM) and peripheral interface adaptor circuits used as part of the computer coupled to a common bidirectional data bus which is coupled to and controlled by a microprocessor unit (MPU) chip. In the digital system, data transfers on the common bidirectional data bus are accomplished without the use of a memory synchronization signal so that a special signal conductor indicating when the memory is ready to transfer data is not required. This is accomplished by logic circuitry which expands a clock signal pulse which is applied to the microprocessor chip whenever a memory location is addressed which has a longer access time than is consistent with the width of the pulse ordinarily applied to the microprocessor to effect its operation.

Abstract: A microprocessor includes a data bus and an address bus. The address bus has first and second sections coupled together in series by bus switch circuitry. The microprocessor also includes control circuitry for controlling various data transfers in the microprocessor. The bus switch circuitry includes a plurality of MOSFETs each having their gate electrodes coupled to the control circuitry and having their sources and drains coupled to corresponding bus conductors of the first and second sections of the address bus. A program counter, incrementer and other working registers are coupled between the address bus first section and the data bus. An accumulator register and an arithmetic logic unit are coupled between the second section of address bus and the data bus. An index register for storing information to be utilized in an indexed addressing mode of operation is coupled to both the first and second sections of the address bus and to the data bus.

Abstract: Interrupt circuitry is provided for an MOS integrated circuit microprocessor chip. An input of the microprocessor chip is adapted to having an external interrupt signal applied thereto for interrupting the operation of the microprocessor chip within a digital data processing system. The input is coupled to circuitry which inhibits loading of the next instruction to be executed in response to an interrupt request signal applied to the interrupt request input, and also forces a code into the instruction register in response to the interrupt request signal. The code is substantially similar to the code for a software wait instruction or a software interrupt instruction. Therefore, much of the same circuitry within the microprocessor can be used for executing an interrupt operation, a software wait instruction, or a software interrupt instruction.

Abstract: A method of generating addresses in a microprocessor includes steps of storing first informationrepresentative of a first address in a first register, such as a program counter register. The first information is transmitted to a first address bus in order to effect addressing the contents of a first location represented by the first address. The first information is also transmitted via the address bus to an incrementor-decrementor circuit. The first information is incremented to produce second information representative of the address of the next instruction during the addressing of the first location. The second information is then transmitted to the first register.

Abstract: A processor including a first bus, a second bus, and a control circuit for producing control signals includes a counter having a plurality of inputs and outputs responsive to the control circuit and coupled between the first and second buses for incrementing digital information present at the inputs of the counter. The processor includes a first coupling circuit responsive to the control circuit for coupling the counter inputs to the first bus to effect transferring digital information from the first bus to the counter inputs. A second coupling circuit couples the counter inputs to the second bus to transfer digital information from the second bus to the counter inputs in response to the control circuit. A third coupling circuit couples the counter outputs to the second bus to transfer digital information from the counter output to the second bus.

Abstract: An interface adaptor suitable for use in a microprocessor system includes an input register coupled to a bidirectional data bus of the microprocessor system. The interface adaptor includes a plurality of registers, including a control register and a data register, coupled to the input register by means of an internal input bus. Each of the plurality of registers includes flip-flops which are coupled as slave flip-flops to corresponding flip-flops of the input register. The corresponding flip-flops of the input register function as master flip-flops. The interface adaptor also includes register selection logic circuitry for selecting one of the plurality of registers by electrically coupling its slave flip-flop to the corresponding master flip-flops of the input register.

Abstract: A microprocessor includes a data bus and an address bus. The address bus has first and second sections coupled together in series by bus switch circuitry. The microprocessor also includes control circuitry for controlling various data transfers in the microprocessor. The bus switch circuitry includes a plurality of MOSFETs each having their gate electrodes coupled to the control circuitry and having their sources and drains coupled to corresponding bus conductors of the first and second sections of the address bus. A program counter, incrementer and other working registers are coupled between the address bus first section and the data bus. An accumulator register and an arithmetic logic unit are coupled between the second section of address bus and the data bus.

Abstract: Interrupt circuitry is provided for an MOS integrated circuit microprocessor chip. An input of the microprocessor chip is adapted to having an external interrupt signal applied thereto for interrupting the operation of the microprocessor chip within a digital data processing system. This first input is connected to circuitry which is enabled by a signal from a bit of a condition code register on the microprocessor chip which bit, is set, acts to mask or disenable the interrupt signal, so that the instruction execution operation of the microprocessor chip is not interrupted. A second input of a microprocessor chip is adapted to having a second interrupt signal applied thereto. The second input is connected to other input circuitry which is not enabled by the mask bit of a condition code register. Therefore, the second input acts as a non-maskable interrupt input.

Abstract: A digital system comprises a plurality of metal-oxide-semiconductors (MOS) chip random access memory (RAM) and read only memory (ROM) and peripheral interface adaptor circuits used as part of the computer coupled to a common bidirectional data bus which is coupled to and controlled by a microprocessor unit (MPU) chip. The digital system uses a multi-level interrupt circuit arrangement including a masked interrupt request input responsive to a multi-plexed interrupt request from peripheral circuits of the system and a non-masked interrupt request input which activates circuitry internal to the microprocessor chip for bypassing program control in initiating an interrupt sequence.

Abstract: A program register is coupled between a data bus N bits wide and an address bus N bits wide for storing the address of the current byte of a multi-byte instruction currently being executed. A counter is also coupled between the address bus and the data bus and is additionally coupled to a program register to allow loading of the counter contents into the program register independently of the status of the address bus. An auxiliary register is also coupled between the address bus and the data bus. The counter is updated every machine cycle during execution of the instruction, except for certain instructions during which the counter is inhibited to allow it to function as an auxiliary register, thereby storing the address of the next instruction. For certain instructions, the address bus is utilized for data transfers to or from the auxiliary register simultaneously with loading of the program register from the counter, depending on the type of instruction being executed.

Abstract: Interrupt circuitry is provided for an MOS integrated circuit microprocessor chip. An input of the microprocessor chip is adapted to having an external interrupt signal applied thereto for interrupting the operation of the microprocessor chip within a digital data processing system. This first input is connected to circuitry which is enabled by a signal from a bit of a condition code register on the microprocessor chip which bit, is set, acts to mask or disenable the interrupt signal, so that the instruction execution operation of the microprocessor chip is not interrupted. A second input of a microprocessor chip is adapted to having a second interrupt signal applied thereto. The second input is connected to other input circuitry which is not enabled by the mask bit of a condition code register. Therefore, the second input acts as a non-maskable interrupt input.