Configuration Handbook - Kamami.pl

Configuration SchemesFigure 13–6. Configuring Multiple Devices Using a Serial Configuration Device (AS)(1) V CC (1) V CC (1)10 kΩ10 kΩ10 kΩSerial ConfigurationDeviceCyclone FPGA MasternSTATUSCONF_DONECyclone FPGA SlavenSTATUSCONF_DONEnCEON.C.nCEV CCnCONFIG nCONFIGnCEOnCEDATADCLKnCSASDIGNDDATA0DCLKnCSOASDOMSEL1MSEL0GNDDATA0DCLKMSEL1MSEL0V CCGNDNote to Figure 13–6:(1) Connect the pull-up resistors to a 3.3-V supply.As shown in Figure 13–6, the nSTATUS and CONF_DONE pins on all targetFPGAs are connected together with external pull-up resistors. These pinsare open-drain bidirectional pins on the FPGAs. When the first deviceasserts nCEO (after receiving all of its configuration data), it releases itsCONF_DONE pin. But the subsequent devices in the chain keep this sharedCONF_DONE line low until they have received their configuration data.When all target FPGAs in the chain have received their configuration dataand have released CONF_DONE, the pull-up resistor drives a high level onthis line and all devices simultaneously enter initialization mode. If anerror occurs at any point during configuration, the nSTATUS line isdriven low by the failing FPGA. If you enable the Auto RestartConfiguration on Frame Error option, reconfiguration of the entire chainbegins after a reset time-out period (a maximum of 40 μs). If the option isturned off, the external system must monitor nSTATUS for errors andthen pulse nCONFIG low to restart configuration. The external system canpulse nCONFIG if it is under system control rather than tied to V CC .1 While you can cascade Cyclone FPGAs, serial configurationdevices cannot be cascaded or chained together.13–12 Altera CorporationCyclone Device Handbook, Volume 1 January 2007