1. Home
  2. Field-Programmable Gate Arrays
  3. VHDL in Xilinx : why this signal is regarded as Global Clock ?

VHDL in Xilinx : why this signal is regarded as Global Clock ?

Hi, all

Here are two processes: One is temporary buffer to acquire transient / real-time input data; the other is another buffer to store every 11 samples; when 11 samples are filled in ChipBuffer_temp, BufferReady is asserted in the first process.

My problem is : expcept the clock signal ChEst_Clk1x, the BufferReady is also treated as Global Clock in Xilinx Constraints Editer, which is not desired. To my understanding, the signal with rising or falling event will be regarded as Clock...., but here I don't know why BufferReady is put in the Global list , and how can I avoid this ?

Many thanks.

ChipInput: process(ChEst_Reset,ChEst_Clk1x)

begin

if ChEst_Reset = '1' then

ChipBuffer_temp (others => '0'));

ChipCount

Reply to
Jimmy
Loading thread data ...

Hi Jimmy,

We've run into similar difficulties. The Xilinx tools will assume, by default, that anything connected to a clock input is connected to a global clock input.

The workaround is to explicitly connect the input pin to an IBUF primitive, and connect the IBUF output to everything that uses the input signal.

For more information, get the Xilinx Libraries Guide.

Here's a link for the PDF version for V6.1 ISE.

formatting link

Here's a link for the online HTML version for V6.1 ISE

formatting link

Other versions are available, but you'll need to search for what you require.

Best regards, Dwayne Surdu-Miller

Reply to
Dwayne Surdu-Miller

P.S. I dunno off-hand why BufferReady is deigned to be a global clock.

One way to find out would be to synthesize the module then view the RTL schematic of the synthesized design and search for anything that connects BufferReady to a clock input. If XST found implications that BufferReady is a clock, the RTL schematic should help you find where the implications took place.

Dwayne Surdu-Miller

Reply to
Dwayne Surdu-Miller

P.P.S. It looks like BufferReady should be an output, not an input (my apologies). It shouldn't be on a global clock pin at all, as they are input-only! Something weird is happening.

Reply to
Dwayne Surdu-Miller

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.