| 摘要 |
A voltage source is configured to produce a desired voltage and the desired voltage is applied to a programmable cell coupled to the voltage source. Configuration may be accomplished by loading a register with a programmed voltage value which may be received as a serial data stream through a test access port coupled to the register. For one embodiment, the voltage source may be coupled to a gate of the programmable cell, thus allowing testing of margin voltages of the programmable cell. In a further embodiment, the voltage source may be coupled to a drain of the programmable cell through a load line circuit, thus providing a programmed voltage for the programmable cell. In general then, the programmable voltage source is configurable to provide a voltage to the programmable cell in accordance with a programmed voltage value loaded into the programmable voltage source. The present invention may be embodied in a programmable device such as a PLD a CPLD or an FPGA and provides easily adjustable verify and/or program voltages, configurable through use of the programmable register, to test the operation of the programmable cell. The higher the bit count of the register, the more precise a verify and/or program voltage that may be provided.
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