Scratch VHDL
The purpose of "Scratch VHDL" is to make reprogrammable logic design into child's play. Sounds ambitious.
Binary Counter
The code uses an integer, a conversion function then creates the 4-bit binary value to be displayed. The integer’s value needs to be constrained to the range 0..15 and the counter roll-over managed. What happens if the count range is unconstrained, even if the roll-over value is managed correctly? Two buttons operate start and stop.
No its not rocket science, some people may not be familiar. It could prove a useful revision for some of the later demonstrations.
Decimal to Binary Conversion Table.
| Decimal | Hexadecimal | Binary |
|---|---|---|
| 0 | 0 | 0000 |
| 1 | 1 | 0001 |
| 2 | 2 | 0010 |
| 3 | 3 | 0011 |
| 4 | 4 | 0100 |
| 5 | 5 | 0101 |
| 6 | 6 | 0110 |
| 7 | 7 | 0111 |
| 8 | 8 | 1000 |
| 9 | 9 | 1001 |
| 10 | A | 1010 |
| 11 | B | 1011 |
| 12 | C | 1101 |
| 13 | D | 1101 |
| 14 | E | 1110 |
| 15 | F | 1111 |
NB. Hexadecimal is just a way of writing groups of 4 binary bits, and is easier to read by comparison with very long binary values. You may have seen them used in Network cards for the Ethernet MAC Address or in checksums (e.g. CRC32).