Vlsi Technology, Inc.

Tein-Yow Yu

Ned D Garinger

Kenneth P Caviasca

James B Nolan

W Henry Potts

Pratiksh Parikh

Level trigger mode interrupts are converted to edge trigger mode interrupts in a computer system. A circuit detects the occurrence of a level trigger mode interrupt request, and asserts an edge trigger mode interrupt request output. The edge trigger mode interrupt request remains asserted until an End of Interrupt input is asserted, indicating that the CPU has completed servicing the prior interrupt. The edge trigger mode interrupt request is then deasserted.

Circuit and method for converting interrupt signals from level trigger

A method and system for testing a digital counter of mn bits comprises dividing the counter into m segments, each of n bits. For test purposes, the counter then is further divided into first and second m segment groups. Multiplex gates are used between the segments and are controlled by sensing the condition of the most significant bits of the most significant one of the m segments for applying clock pulses to verify specific connections between various bits of the counter for the first four cycles of clock pulses applied during the test mode. After these four cycles, gating circuits coupled with the most significant bits of the most significant one of the m segments are used to automatically switch the remainder of the test connections to the second group to verify all of the remaining connections in the counter, with full testing of the counter being accomplished in 2.sup.n +2 cycles of clock pulses.

Dynamic division system and method for improving testability of a counter

A circuit generates a system clock signal. On a first input of the circuit a first oscillating signal is placed. On a second input, a second oscillating signal may be placed. Clock sense logic is connected to the second input. The clock sense logic detects whether the second oscillation signal is present on the second input. When the second oscillating signal is not present on the second input, the first oscillating signal is selected to be used to generate the system clock. When the second oscillating signal is present on the second input, the second oscillating signal is selected to be used to generate the system clock. The selected oscillating signal is divided to produce the system clock signal. A first frequency divider divides the selected oscillating signal by a first amount. In parallel, a second frequency divider divides the selected oscillating signal by a second amount. A selector, for example, a multiplexor, selects output from either the first frequency divider or the second frequency divider as the system clock signal. When the first oscillating signal is being used to generate the system clock, the second input may be used to control the selection of frequency dividers.

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Chandler, AZ, United States of America

Tein-Yow Yu