EPP interface using Altera FPGA

[Michele Bergo]

I want to realize an EPP interface using Altera FPGA Cyclone (read and write
operation) but I have some synchronization problems. I want to sample datas
from a 4 bits chip, storing them in a ZBT SRAM memory (Flow trought) and
later acquiring them by parallel port. the chip works at 10MHz but the pll
on board can't divide input clock of 20MHz for 2. How can I divide the
frequency?
thanks. Does anyone do something like that?

 

[Ralf Hildebrandt]

Michele Bergo wrote:

the chip works at 10MHz but the pll
on board can't divide input clock of 20MHz for 2. How can I divide the
frequency?

Is it really so simple?

process(reset,clk_in)
begin
if (reset='1') then
clk_out='0'; -- or '1' - whatever you want
elsif rising_edge(clk_in) then
clk_out<=NOT(clk_out);
end if;
end process;

If clk_out has to drive many cells, clock skew on the FPGA may be a
problem. Therefore depending on the FPGA you may instantiate a clock
buffer, that buffers clk_out. Read the manual for you FPGA how to do it.
Often it will be a simple component that has to be instantiated with
input clk_out.


Ralf

 

[Michele Bergo]

Thank u very much.

Michele Bergo wrote:



Is it really so simple?

process(reset,clk_in)
begin
if (reset='1') then
clk_out='0'; -- or '1' - whatever you want
elsif rising_edge(clk_in) then
clk_out<=NOT(clk_out);
end if;
end process;

If clk_out has to drive many cells, clock skew on the FPGA may be a
problem. Therefore depending on the FPGA you may instantiate a clock
buffer, that buffers clk_out. Read the manual for you FPGA how to do it.
Often it will be a simple component that has to be instantiated with
input clk_out.


Ralf

 

[Yann KERNIN]

Hi,

I'm also interrested with the EPP protocol to develop it in a Xilinx FPGA.

Something I don't know is what system manage the DIR pin of the
interface chip (computer or FPGA). If, it is the FPGA, what are the
timing concerning this signal.

Thanks
Yann

Michele Bergo a écrit :

 

[Mike Treseler]

I'm also interrested with the EPP protocol to develop it in a Xilinx FPGA.

Something I don't know is what system manage the DIR pin of the
interface chip (computer or FPGA). If, it is the FPGA, what are the
timing concerning this signal.

http://www.google.com/search?q=EPP+signal+definitions

-- Mike Treseler