Patent ID: 7191352

Claim:
A control circuit for enabling a host to control a power cut-off protection circuit, the protection circuit being adapted for preventing damage to a level-shifter when power to a peripheral is cut-off, the level-shifter for providing level-shifted signals and for coupling with the peripheral, the control circuit being suitable for use in a graphics controller that includes the level-shifter and the power cut-off protection circuit, the power cut-off protection circuit being coupled with the level-shifter and having a protection-circuit-control input for selecting one of first and second control states, the control circuit comprising: a memory pair including: a polarity-selecting input, a first storage element having an input, a first storage output, an initial-state input coupled with the polarity-selecting input, and being adapted to respond to a particular indication on the initial-state input by outputting a first predetermined indication, a second storage element having an input, a second storage output, an initial-state input coupled with the polarity-selecting input, and being adapted to respond to the particular indication on the initial-state input by outputting a second predetermined indication; and a first selecting circuit having first and second selecting-circuit inputs coupled respectively with the first and second storage outputs, an output coupled with the protection-circuit-control input, and a selecting input coupled with the host for selecting one of the first and second selecting-circuit inputs, wherein the control circuit thereby enables the host to control the power cut-off protection circuit following an assertion of the particular indication; and wherein the particular indication is a reset indication, the control circuit further comprises a reset-generating apparatus for generating the reset indication, and wherein the reset-generating apparatus is further adapted to generate the reset indication in response to a reset indication internally generated by the graphics controller.