Conversions

Binary to Bcd - Bcd to Binary

	Please check this site: http://www.doulos.com/knowhow/vhdl_designers_guide/models/binary_bcd/
	The ideas of Bin to Bcd conversions can be found at this "old" document: XAPP029

	Its possible to convert a Binary to Bcd values (and the other way around), with a "slightly modified" 4-bit shift register (one for each Bcd-number).
		After the shift Before the shift Bcd_x+1 (next bit) Bcd_x <= Bcd_x+1 (next bit) Bcd_x0 (0) 0 <= 0 (0) 0 hence 0 <= 0 * 2 0 (0) 2 <= 0 (0) 1 hence 2 <= 1 * 2 0 (0) 4 <= 0 (0) 2 hence 4 <= 2 * 2 0 (1) 6 <= 0 (0) 3 hence 6 <= 3 * 2 0 (1) 8 <= 0 (0) 4 hence 8 <= 4 * 2 1 (0) 0 <= 0 (1) 5 hence 10 <= 5 * 2 1 (0) 2 <= 0 (1) 6 hence 12 <= 6 * 2 1 (0) 4 <= 0 (1) 7 hence 14 <= 7 * 2 1 (1) 6 <= 0 (1) 8 hence 16 <= 8 * 2 1 (1) 8 <= 0 (1) 9 hence 18 <= 9 * 2

Layout for a x-bit binary to 5 digit Bcd converter.

	The principle in a Binary to Bcd conversion 0000 -0- 0000 -0- 0000 -0- 0000 -0- 0000 <= 11101110 0000 -0- 0000 -0- 0000 -0- 0000 -0- 0001 <= 11011100 0000 -0- 0000 -0- 0000 -0- 0000 -0- 0011 <= 10111000 0000 -0- 0000 -0- 0000 -0- 0000 -1- 0111 <= 01110000 0000 -0- 0000 -0- 0000 -0- 0001 -0- 0100 <= 11100000 0000 -0- 0000 -0- 0000 -0- 0010 -1- 1001 <= 11000000 0000 -0- 0000 -0- 0000 -1- 0101 -1- 1001 <= 10000000 0000 -0- 0000 -0- 0001 -0- 0001 -1- 1001 <= 00000000 0000 -0- 0000 -0- 0010 -0- 0011 -1- 1000 <= 00000000 0 0 2 3 8 11101110₂ = 128+64+32 +8+4+2 = 255 -16-1 = 238

A possible solution to the "modified shift register" for Binary to Bcd and vice versa.