Abstract: A method and apparatus allowing two independent arbiters which do not directly talk to one another to function on a common system bus, allowing efficient operation of a master controller, and virtually endless capability to add peripherals to the common system bus without problems or major modifications commonly associated with additional arbitration overhead. A master controller sets time slot parameters for an external, subordinate arbiter as often as desired. Based on the time slot parameter information, the subordinate arbiter functions on an electrically separated portion of the common system bus during all times but for a time slot associated with communication of the super arbiter over the entire common system bus. During this time, a tri-state buffer element allows communication between portions of the common system bus.

Abstract: A method and apparatus allowing two independent arbiters which do not directly talk to one another to function on a common system bus, allowing efficient operation of a master controller, and virtually endless capability to add peripherals to the common system bus without problems or major modifications commonly associated with additional arbitration overhead. A master controller sets time slot parameters for an external, subordinate arbiter as often as desired. Based on the time slot parameter information, the subordinate arbiter functions on an electrically separated portion of the common system bus during all times but for a time slot associated with communication of the super arbiter over the entire common system bus. During this time, a tri-state buffer element allows communication between portions of the common system bus.

Abstract: A method and apparatus allowing efficient access control to a common data bus by including an isolation device to separate the common data bus, a priority-based arbiter to control access to the internal portion of the common data bus including a processor or other bus master, and a time slot arbiter to control access to the external portion of the common data bus including multiple bus masters, an external memory interface, etc. The common external memory may be allocated for exclusive or non-exclusive use by the various devices utilizing either portion of the isolated common data bus. External devices accessing the external memory may communicate directly with one or more bus masters, e.g., on the internal portion of the common data bus.

Abstract: An instruction clock of a processing unit in a low power mode in accordance with the principles of the present invention is qualified with a burst mode control signal. The burst mode control signal is allowed to start and stop the instruction flow of the relevant processing unit. In the disclosed embodiment, a master clock signal is qualified by a clock control circuit to provide bursts of an instruction clock signal to the relevant processing unit. To operate the burst instruction cycle control unit, a user pre-programs a burst length, into a register to set the length of the burst of instruction cycles to the relevant processing unit. A maximum counter value in a counter sets the period of the instruction cycle bursts provided to the relevant processing unit.

Abstract: An integrated circuit counter is capable of implementing a relatively high count while being testable using a relatively low number of clock cycles. A linear-feedback shift register (LFSR) having n bit positions is used as the counter. The feedback path of the shift register includes an exclusive OR (XOR) gate that couples selected bits back to the input of the register, in order to implement a 2.sup.n -1 counter. Combinatorial logic circuitry is included to test the counter in significantly less than 2.sup.n -1 clock cycles. This allows for implementing a testable "watchdog timer" that may be used to detect software runaway conditions in microprocessor systems, among other uses.