lib/include/prjxray/xilinx/xc7series/ecc.h

#ifndef PRJXRAY_LIB_XILINX_XC7SERIES_ECC_H_
#define PRJXRAY_LIB_XILINX_XC7SERIES_ECC_H_

#include <cstdint>

namespace prjxray {
namespace xilinx {
namespace xc7series {

// Extend the current ECC code with one data word (32 bit) at a given
// word index in the configuration frame and return the new ECC code.

uint32_t icap_ecc(uint32_t idx, uint32_t data, uint32_t ecc) {
	uint32_t val = idx * 32;  // bit offset

	if (idx > 0x25)  // avoid 0x800
		val += 0x1360;
	else if (idx > 0x6)  // avoid 0x400
		val += 0x1340;
	else  // avoid lower
		val += 0x1320;

	if (idx == 0x32)  // mask ECC
		data &= 0xFFFFE000;

	for (int i = 0; i < 32; i++) {
		if (data & 1)
			ecc ^= val + i;

		data >>= 1;
	}

	if (idx == 0x64) {  // last index
		uint32_t v = ecc & 0xFFF;
		v ^= v >> 8;
		v ^= v >> 4;
		v ^= v >> 2;
		v ^= v >> 1;
		ecc ^= (v & 1) << 12;  // parity
	}

	return ecc;
}

}  // namespace xc7series
}  // namespace xilinx
}  // namespace prjxray

#endif  // PRJXRAY_LIB_XILINX_XC7SERIES_ECC_H_