Configuration Handbook - Kamami.pl

Configuring APEX 20KE & APEX 20KC DevicesWhen using enhanced configuration devices or EPC2 devices, nCONFIGof the FPGA can be connected to nINIT_CONF, which allows theINIT_CONF JTAG instruction to initiate FPGA configuration. ThenINIT_CONF pin does not need to be connected if its functionality is notused. An internal pull-up resistor on the nINIT_CONF pin is alwaysactive in the enhanced configuration devices and the EPC2 devices,which means an external pull-up resistor is not required if nCONFIG istied to nINIT_CONF. Since a 10-kΩ pull-up resistor to V CCINT is requiredto successfully configure APEX 20KE devices, you need to isolate the1.8-V V CCINT from the configuration device’s 3.3-V supply. To isolate the1.8-V and 3.3-V power supplies, add a diode between the APEX 20KEdevice’s nCONFIG pin and the configuration device’s nINIT_CONF pin.Select a diode with a threshold voltage (V T ) less than or equal to 0.7 V. Thediode will make the nINIT_CONF pin an open-drain pin; the pin will onlybe able to drive low or tri-state. If nINIT_CONF is not used or notavailable (e.g., on EPC1 devices), nCONFIG must be pulled to V CCINTthrough a 10 kΩ resistor and the isolating diode is not needed. If multipleEPC2 devices are used to configure an APEX 20KE or APEX 20KCdevice(s), only the first EPC2 has its nINIT_CONF pin tied to the device’snCONFIG pin.You can use a single configuration chain to configure APEX 20KE andAPEX 20KC devices with other Altera devices. To ensure that all devicesin the chain complete configuration at the same time or that an errorflagged by one device initiates reconfiguration in all devices, all of thedevice CONF_DONE and nSTATUS pins must be tied together.fFor more information on configuring multiple Altera devices in the sameconfiguration chain, refer to Configuring Mixed Altera FPGA Chains in theConfiguration Handbook.Figure 7–8 shows the timing waveform for the PS configuration schemeusing a configuration device.Altera Corporation 7–19August 2005 Configuration Handbook, Volume 1