Data processing: structural design – modeling – simulation – and em – Emulation – In-circuit emulator
Reexamination Certificate
1998-05-18
2001-02-06
Teska, Kevin J. (Department: 2763)
Data processing: structural design, modeling, simulation, and em
Emulation
In-circuit emulator
C712S227000, C714S028000
Reexamination Certificate
active
06185522
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a method for emulating a non-bond-out version of a microcontroller that has standard port, such as disclosed in U.S. Pat. No. 5,574,852 assigned to the same assignee as in this application, which patent is hereby incorporated by reference. At present, the in-circuit emulation of many microcontrollers, such as, but not being limited, to use with the well-known 80C51 microcontroller, requires the presence of at least two 8-bit IO-ports. One port, usually port P0, is then used as a multiplexed 8 bit low address/data bus, whereas the another one, normally port P2, provides the high bits of the 16 bit address space. Since both of these ports therewith will have lost their standard IO-facility, this IO facility must be reconstructed externally from the chip. The data that is necessary for the P0, P2 reconstruction is then supplied in multiplexed fashion via the P0, P2 lines. This needs to be done only in emulation mode, because in normal mode the port lines operate in a manner that has been defined specifically for the microcontroller in question. Further, restricting the operation to 8-bit memory addresses would be out of the question. For many microcontroller applications that need only limited IO, the cost of two ports has been found excessive.
SUMMARY TO THE INVENTION
In consequence, amongst other things, it is an object of the present invention to provide facilities to allow emulation of a microcontroller that has a program memory space which needs more address bits than according to the width of the parallel port.
The invention provides a method for emulating a microcontroller having an internal multiplexer and an IO port. According to an embodiment of the invention, the method comprises the steps of latching program latching program store addresses into the microcontroller via the IO port; multiplexing, using the internal multiplexer, user data and the program store addresses input to the microcontroller via the IO port; synchronizing the microcontroller according to a predefined machine cycle having a plurality of states, each of which comprises at least two clock pulses; and outputting, from the IO port, mutually exclusive parts of a program store address in a machine state of the machine cycle for external evaluation of the address.
The invention also relates to a microcontroller allowing such emulation, and to an emulation system arranged for executing the method according to the invention. Other objects and attainments together with a fuller understanding of the invention will become apparent and appreciated by referring to the following description and claims taken in conjunction with the accompanying drawings.
REFERENCES:
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PCT search report, PCT/IB98/00536.
Choi Kyle J.
Teska Kevin J.
U.S. Philips Corporation
Wieghaus Brian J.
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