Atmel makes EEPROM-based devices that they claim are pin compatible
with Xilinx 1700 devices. They are named in a similar fashion as Xilinx
PROMs-- 17Cxxx-- 17C65, 17C128, for example. Although they are pin-
compatible, they are not design-compatible.
Xilinx has not qualified these parts for use in configuring Xilinx FPGAs.
Although the Atmel parts are spec'd the same, there are some
significant differences between the Atmel EEPROMs and Xilinx
1. Atmel PROMs are not compatible with Xilinx FPGA Express
Mode configuration because they are not fast enough.
2. There is incompatibility in how pin 7 (VPP), the
programming voltage pin, is connected to Vcc. During
operation, this pin must be connected to VCC for Xilinx serial
PROMs. Atmel uses the same pin as an active low serial
enable input for in system reprogramming. Because of this
difference, the Atmel parts cannot be considered as drop-in