- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
I realise that the DM9000 chip needs a 25 Mhz clock from a PLL, but I'm confused about how to actually deliver it and handle the other signals.
I would think you could use a PLL like so: pll: sdram_pll PORT MAP (CLOCK_50, DRAM_CLK, ENET_CLK);
Which would connect the -3 ns output of the PLL to the SDRAM and the divided-by-2 output to the Ethernet chip. The DE2_NET example, however, has the following port maps: // the_DM9000A
.ENET_CLK_from_the_DM9000A(ENET_CLK),
....
.iOSC_50_to_the_DM9000A(CLOCK_50),
There is also a PLL which has a 25 Mhz output, but I can't find a place where it connects to the Ethernet chip. If somebody can clear this up it would be much appreciated.
Link Copied
1 Reply
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
--- Quote Start --- originally posted by benway@Mar 17 2007, 05:49 PM i realise that the dm9000 chip needs a 25 mhz clock from a pll, but i'm confused about how to actually deliver it and handle the other signals.
i would think you could use a pll like so:
pll: sdram_pll port map (clock_50, dram_clk, enet_clk);
which would connect the -3 ns output of the pll to the sdram and the divided-by-2 output to the ethernet chip.
the de2_net example, however, has the following port maps:
// the_dm9000a
.enet_clk_from_the_dm9000a(enet_clk),
....
.iosc_50_to_the_dm9000a(clock_50),
there is also a pll which has a 25 mhz output, but i can't find a place where it connects to the ethernet chip. if somebody can clear this up it would be much appreciated.
<div align='right'><{post_snapback}> (index.php?act=findpost&pid=22309)</div> --- Quote End --- In the DE2_NET project, the ENET_CLK signal is generated in the DMA9000A_IF.v file, by using a simple divider from a 50Mhz signal to get a 25MHz signal. I agree that it is better to use a PLL to generate the ENET_CLK signal. So you can probably go with PLL code you have.
Reply
Topic Options
- Subscribe to RSS Feed
- Mark Topic as New
- Mark Topic as Read
- Float this Topic for Current User
- Bookmark
- Subscribe
- Printer Friendly Page