A programmable logic integrated circuit device utilizes volatile memory elements such as SRAM for retaining configuration information. A circuit is provided as part of the device for detecting loss of power on a supply input pin. When power loss is detected, a backup voltage supply, packaged with the...http://www.google.com.tw/patents/US5121359?utm_source=gb-gplus-share專利 US5121359 - Configuration memory for programmable logic device
