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Browse Prior Art Database

Stop-On-Address Capability for a Single-Chip Microprocessor

IP.com Disclosure Number: IPCOM000042982D
Original Publication Date: 1984-Jun-01
Included in the Prior Art Database: 2005-Feb-04
Document File: 1 page(s) / 13K

Publishing Venue

IBM

Related People

Hester, PD: AUTHOR [+2]

Abstract

The stop-on-address function, a major debugging aid, is difficult due to processor chip pin limitations. The technique described in this article represents a hardware-based stop-on-address capability implemented on a single-chip microprocessor, completely contained on the chip and requiring no extra module pins. The ability to stop a microprocessor system on a particular instruction is a quite powerful hardware debugging aid. However, such a function is difficult to implement due to pin limitations on the processor chip. The most common method of overcoming this difficulty is to employ logic external to the chip to monitor processor instruction fetch addresses and to stop the system when the desired address is encountered.

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Stop-On-Address Capability for a Single-Chip Microprocessor

The stop-on-address function, a major debugging aid, is difficult due to processor chip pin limitations. The technique described in this article represents a hardware-based stop-on-address capability implemented on a single-chip microprocessor, completely contained on the chip and requiring no extra module pins. The ability to stop a microprocessor system on a particular instruction is a quite powerful hardware debugging aid. However, such a function is difficult to implement due to pin limitations on the processor chip. The most common method of overcoming this difficulty is to employ logic external to the chip to monitor processor instruction fetch addresses and to stop the system when the desired address is encountered. However, this approach incurs the expense of the external hardware required, and has only limited usefulness in systems where instruction fetches are highly decoupled from instruction execution. The method presented in this article, involving implementation of a stop-on-address capability for a single-chip microprocessor, entails having the function embedded, i.e., contained within the chip rather than being implemented via off- chip means. The basic concept recognizes the fact that, in order to implement such an on-chip stop-on-address function, some additional circuitry must be formed on the chip, including a register of sufficient size to hold a complete address and control information (about 34 bits), in which the selected address can be stored, and comparative circuitry for comparing the stored address with the actual machine address. In addition, circuitry is required for loading the selected address into the register. In a single-chip microprocessor, where I/O pins are extremely scarce, an ar...