Claims
- 1. A microcontroller fabricated on a semiconductor chip, and configurable to any of a plurality of operating modes to execute programs and instructions and, in response to the execution of the programs and instructions, to generate control signals to selectively control external apparatus, said microcontroller comprising:
- an on-chip EPROM program memory,
- EPROM fuses occupying a predetermined number of address locations of said on-chip EPROM program memory for storing a binary value of a bit, each of said EPROM fuses having at any given time either one of two different states defined as blown or not blown according to the value of the bit stored in a respective address location of said on-chip EPROM program memory,
- configuration means including predetermined ones of said EPROM fuses for configuring the microcontroller in desired ones of said plurality of operating modes according to which of the two different states is occupied by respective said predetermined ones of said EPROM fuses, and
- test means for testing the microcontroller in said operating modes, said test means including means for emulating said predetermined ones of said EPROM fuses to configure the microcontroller in operating modes for test purposes without using said predetermined ones of said EPROM fuses.
- 2. The microcontroller of claim 1, wherein:
- the test means includes means for suppressing a change of state of said predetermined ones of said EPROM fuses during testing of the microcontroller in said operating modes.
- 3. The microcontroller of claim 1, wherein:
- the emulating means includes a plurality of programmable latches.
- 4. The microcontroller of claim 1, further including:
- means responsive to completion of testing of the microcontroller for inhibiting the means for emulating of the test means from continuing to emulate said predetermined ones of said EPROM fuses.
- 5. A method of testing a microcontroller fabricated on a semiconductor chip, and having an on-chip EPROM program memory, wherein the microcontroller is configurable to any one of a plurality of operating modes according to which of two different fuse states are occupied by respective selected ones of a plurality of programmable EPROM configuration fuses mapped in the on-chip EPROM program memory at predetermined address locations of said on-chip EPROM program memory, each of the predetermined address locations for storing either of two different values of a bit, wherein the fuse state of each of said EPROM configuration fuses is defined as blown or not blown according to the value of the bit stored in a respective address location of said on-chip EPROM program memory, said method comprising the steps of:
- configuring the microcontroller in any desired one of said operating modes for testing the microcontroller in a desired one of said operating modes, the step of configuring the microcontroller being performed using latches emulating preselected ones of said EPROM fuses, and
- confining the testing of the microcontroller to a microcontroller operating mode in which the microcontroller is configured with said latches rather than with any of said EPROM fuses.
- 6. The method of claim 5, further including the step of:
- suppressing programming of fuse state of said EPROM configuration fuses during the step of testing.
- 7. The method of claim 5, further including the step of:
- removing the configuring of the microcontroller in a desired operating mode with said latches after completion of the testing step, and
- thereafter reconfiguring the microcontroller to a tested one of said operating modes previously configured using latches, by substituting preselected ones of said EPROM configuration fuses with programmed fuse states for said latches.
- 8. In a microcontroller fabricated on a semiconductor chip, and configurable to any of a plurality of operating modes to selectively control external apparatus, an improvement comprising:
- an electrically programmable memory including programmable fuse means at predetermined address locations of the programmable memory for configuring the microcontroller in any of said plurality of operating modes depending on programming of the programmable fuse means, and
- test means for testing the microcontroller in said plurality of operating modes, the test means including latches and means for substituting the latches for the programmable fuse means to confine testing of the microcontroller in any of said plurality of operating modes to operating modes configured with the latches rather than with the programmable fuse means.
- 9. In the microcontroller improvement of claim 8,
- the test means further including means responsive to completion of testing of the microcontroller in an operating mode configured with the latches, for reconfiguring the microcontroller to the tested operating mode with the programmable fuse means for maintaining said tested operating mode for controlling the external apparatus.
- 10. A semiconductor device capable of being configured in a multiplicity of configurations corresponding to desired potential operating modes for a selected application of the semiconductor device, said semiconductor device comprising:
- programmable fuse means for configuring said semiconductor device in any one of said multiplicity of configurations by suitably programming the programmable fuse means, to provide a permanently programmed desired operating mode for the semiconductor device,
- latch means for replacing the programmable fuse means to permit testing of the semiconductor device in all of said multiplicity of configurations for the selected application, and
- means for substituting the latch means for the programmable fuse means for configuring the semiconductor device in any one of said multiplicity of configurations by using the latch means rather than the programmable fuse means.
Parent Case Info
This application is a continuation of application Ser. No. 07/790,969 filed on Nov. 12, 1991, which is now abandoned.
US Referenced Citations (7)
Continuations (1)
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Number |
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790969 |
Nov 1991 |
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