Rising edge of IN- what does it mean.

[vishal_sonam]

I am new to VHDL so please help me
There are two signals RESET and IN. How should the sensitivity list look like
if a method should be called on a rising edge of IN and on every change of
RESET?

I know about the sensitivity list and I understood the change of RESET also but what mean RISING EDGE OF IN.
Please help me to understand this
Thanks

 

[milan.rajik]

IN is an input pin and rising edge means when pulse goes from low to high. It is the transition from low to high state or in 5V TTL logic level it is transition from 0 to 5V.

 

[ads-ee]

As you didn't post any code as to what you were looking at....

If the code looks like this:

---

Code VHDL - [expand]
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process (clock, reset)
begin
  if (reset = '1') then
    q <= '0';
  elsif rising_edge(clock) then
    q <= d;
  end if;
end process;

---

Then it would be an active high asynchronously reset register with a rising edge clock.

If the code is instead like this:

---

Code VHDL - [expand]
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process (clock)
begin
  if rising_edge(clock) then
    if (reset = '1') then
      q <= '0';
    else
      q <= d;
    end if;
  end if;
end process;

---

Then it would be an active high synchronous reset register with a rising edge clock.

If the IN signal is an input pin (as milan.rajik says) and is going directly to the clock pin of a register, then it better be a clean input with well defined transitions, otherwise you may end up with a circuit that has "glitches".

And that rising_edge thing is a function:

---

Code VHDL - [expand]
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FUNCTION rising_edge  (SIGNAL s : std_ulogic) RETURN BOOLEAN IS
BEGIN
    RETURN (s'EVENT AND (To_X01(s) = '1') AND (To_X01(s'LAST_VALUE) = '0'));
END;

---

 

[vishal_sonam]

this is my program.
This is a system C program.

#ifndef CRC_CALC_H
#define CRC_CALC_H
#include "systemc.h"
#include "iostream"
#include "iomanip"
SC_MODULE(crc_calc) {
	// ports
	sc_in_clk				clk;
	sc_in	< bool >			reset;
	sc_in	< bool >			crc_en;
	sc_in	< bool >			data_in;
	sc_out	< sc_uint <4> >			crc_out;
	// variables
	sc_uint <4>    ep,Q;
	// functions
	void crc4();
	//constructor
	SC_CTOR(crc_calc) 
	{
              SC_METHOD(crc4);
              sensitive << reset << clk.pos();
         }	
};
#endif

so if I take this program does "RISING EDGE OF IN " here IN means by "CLOCK"?