Configuration Handbook - Kamami.pl

Passive Serial ConfigurationIf the Auto-Restart Configuration After Error option is turned on, the FPGAsrelease their nSTATUS pins after a reset time-out period (maximum of 40µs). After all nSTATUS pins are released and pulled high, themicroprocessor can try to reconfigure the chain without needing to pulsenCONFIG low. If this option is turned off, the microprocessor mustgenerate a low-to-high transition (with a low pulse of at least 8 µs) onnCONFIG to restart the configuration process.In your system, you can have multiple devices that contain the sameconfiguration data. To support this configuration scheme, all device nCEinputs are tied to GND, while nCEO pins are left floating. All otherconfiguration pins (nCONFIG, nSTATUS, DCLK, DATA0, and CONF_DONE)are connected to every device in the chain. You should pay specialattention to the configuration signals because they can require bufferingto ensure signal integrity and prevent clock skew problems. Specifically,ensure that the DCLK and DATA lines are buffered for every fourth device.Devices must be the same density and package. All devices will start andcomplete configuration at the same time. Figure 6–11 shows multi-devicePS configuration when both APEX II devices are receiving the sameconfiguration data.Figure 6–11. Multiple-Device PS Configuration Using a Microprocessor When Both FPGAs Receive the SameDataMemoryADDRDATA0VCC (1)VCC (1)1 kΩ 1 kΩAPEX II DeviceAPEX II DeviceCONF_DONEMSEL1MSEL0CONF_DONEMSEL1MSEL0MicroprocessorGNDnSTATUSnCEDATA0nCONFIGGNDnCEO N.C. (2)GNDnSTATUSnCEDATA0nCONFIGGNDnCEO N.C. (2)DCLKDCLKNotes to Figure 6–11:(1) The pull-up resistor should be connected to a supply that provides an acceptable input signal for all devices in thechain.(2) The nCEO pins of both devices are left unconnected when configuring the same configuration data into multipledevices.6–22 Altera CorporationConfiguration Handbook, Volume 1 August 2005