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Is Altera compatible with Xilinx?
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In what way?
1) Generic VHDL/Verilog constructs can be synthesized in Altera Quartus and Xilinx ISE. Each vendor has their own FPGA IP, eg., RAM blocks, counters, etc., but both tools can infer these components from generic VHDL (you just have to follow the vendor's inference guides).
2) At the electrical levels; both have single-ended I/Os, LVDS, high-speed transceivers. These are all compatible.
3) Both have (different) soft-core processors; Altera NIOS II and Xilinx Microblaze. The instruction sets are different, but both can run an OS like uCOS-II and be programmed in C, so arguably code is portable.
They are different, but if you understand how to use one vendor's devices, the major effort in understanding the other vendor, is related to the development tools and IP.
Cheers,
Dave
