DE0 NANO running LED schematic design not running as expected

Altera_Forum · ‎05-10-2016

I just bought a DE0-Nano Development and Education Board from:

This is my first FPGA.

I use Quartus II 32-bit Version 13.0.1 Web Edition

Start with a simple design I made a running LED

- Use the on-board oscillator. PLL and lpm counter to make the frequency lower

- another lpm counter to feed the lpm decode.

- lpm decode to output the running LED

running OK

Then I tried add a DFF to make the running LED bidirectional (see my pic).

- The DFF is controlled by the lpm decode edge output. The DFF output is controlling the lpm counter.

The running LED is not running as I expected. The led7 only ON at startup and never reach back.

So it run with sequence like this from startup:

led7 - led6 - led5 - led4 - led3 - led2 - led1 - led0 - led1 - led2 - led3 - led4 - led5 - led6 - led5 - led4 - ... (not reaching led7)

Something wrong in my design?