Answers Database SPROMS: Configuration: 8-pin sockets w/built-in capacitors can cause multi-prom config problems Record #465 Product Family: Hardware Product Line: 1700 Product Part: 1700 Problem Title: SPROMS: Configuration: 8-pin sockets w/built-in capacitors can cause multi-prom config problems Problem Description: Urgency: Standard General Description: PROMS: 8-pin sockets w/built-in capacitors can cause multi-prom configuration problems. FPGA(s) may not configure when loaded from multiple 8-pin proms because of this. Some 8-pin dip sockets have a capacitor connected from pin 4 to pin 8, the traditional Vcc and gnd connections. These sockets can cause problems in multiple prom setups, The capacitor is connected between Vcc (pin 8) and CE (pin 4). In two-PROM setups, CE of the second PROM and CEO of the first are connected. When CEO goes active low, it take some time for the capacitor to charge, and to allow the line to go low. Meanwhile, CCLK is still running and taking what ever data it sees while the the second PROM is waiting for the CE line to go active low. This will prevent the DONE line from going high because an incorrect bit stream will be seen by the FPGA. Solution 1: Remove the capacitor, or use different sockets. End of Record #465 - Last Modified: 07/29/99 18:42

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