Configuration Handbook - Kamami.pl

Configuring APEX 20KE & APEX 20KC DevicesV CCINT is Powered After V CCIOIf the APEX 20KE device is configured by an external host, such as amicroprocessor, ensure that the configuration controller holds nCONFIGlow during power-up and then drives nCONFIG high when all powersupplies are stable to begin of configuration.If the APEX 20KE device is configured using a configuration device andV CCINT is powered up during or after the configuration device has exitedPOR (released nSTATUS/OE signal), nCONFIG must be tied to V CCINTthrough a 10-kΩ resistor. The configuration device will exit POR 200 ms(maximum) after power-up.When using an enhanced configuration device to configure any AlteraFPGAs, including APEX 20KE devices, the V CCINT of the FPGA must bepowered before the enhanced configuration device exits POR (signaledby the low-to-high transition on the OE/nSTATUS signal). Power upneeds to be controlled so that the enhanced configuration device's OEsignal goes high after the CONF_DONE signal is pulled low.If the FPGA is not powered up after the enhanced configuration deviceexits POR, the CONF_DONE signal will be high since the pull-up resistor ispulling this signal high. When the enhanced configuration device exitsPOR, OE is released and pulled high by a pull-up resistor. If the enhancedconfiguration device sees its nCS/CONF_DONE signal also high, theconfiguration device will go into an idle state because it sees the FPGA isalready configured. DATA and DCLK will not toggle and the enhancedconfiguration device will only exit this idle state if it is powered downand then powered up correctly.To ensure the enhanced configuration device enters configuration modeproperly, you need to ensure that the FPGA completes its power-upbefore the enhanced configuration device exits POR. Alternatively thenSTATUS/OE line can be held low by an open-drain signal until after theV CCINT power supply is stable.fFor more information about power sequencing of enhancedconfiguration devices, refer to the Enhanced Configuration Devices (EPC4,EPC8, & EPC16) Data Sheet in the Configuration Handbook.Altera Corporation 7–69August 2005 Configuration Handbook, Volume 1