구차니의 잡동사니 모음

pi@raspberrypi:~ $ python

Python 2.7.9 (default, Sep 17 2016, 20:26:04)

[GCC 4.9.2] on linux2

Type "help", "copyright", "credits" or "license" for more information.

>>> exit() 

pi@raspberrypi:~ $ pypy

Python 2.7.10 (4.0.1+dfsg-1+rpi1, Mar 07 2016, 10:36:18)

[PyPy 4.0.1 with GCC 4.9.2] on linux2

Type "help", "copyright", "credits" or "license" for more information.

>>>> exit() 

pi@raspberrypi:~ $ which python

/usr/bin/python

pi@raspberrypi:~ $ which pypy

/usr/bin/pypy

pi@raspberrypi:~ $ ll /usr/bin/pypy

lrwxrwxrwx 1 root root 22 Mar  8  2016 /usr/bin/pypy -> ../lib/pypy/bin/pypy-c

pi@raspberrypi:~ $ ll /usr/lib/pypy/bin

total 32604

drwxr-xr-x 2 root root     4096 Nov 26  2016 .

drwxr-xr-x 8 root root     4096 Nov 26  2016 ..

-rwxr-xr-x 1 root root 33374512 Mar  8  2016 pypy-c

#5 // dealy 5ns

# 10; // wait 10 ns;

w <= #4 a ^ b;

x <= #5 b | c; 

module-name #(parameter-assignment) instance-name (module-terminal-list) ; 

//#include <stdio.h>

/*

 * hello.c

 */

int main(void) {

// printf("Hello World!\n");

return 0;

} 

char * const a;

means that the pointer is constant and immutable but the pointed data is not.

You could use const_cast(in C++) or c-style cast to cast away the constness in this case as data itself is not constant.

const char * a;

means that the pointed data cannot be written to using the pointer a. Using a const_cast(C++) or c-style cast to cast away the constness in this case causes Undefined Behavior. 

module dff (clk, d, q);

input clk, d;
output q;
reg q;
always @(posedge clk) q = d;
endmodule
 
module top;
reg data, clock;
wire q_out, net_1;
  dff inst_1 (.d(data), .q(net_1), .clk(clock));
  dff inst_2 (.clk(clock), .d(net_1), .q(q_out));
endmodule

module dff (clk, d, q);

input clk, d;
output q;
reg q;
always @(posedge clk) q = d;
endmodule
 
module top;
reg data, clock;
wire q_out, net_1;
  dff inst_1 (clock, data, net_1);
  dff inst_2 (clock, net_1, q_out);
endmodule

example 1

module dff (clk, d, q);
input clk, d;
output q;
reg q;
always @(posedge clk) q = d;
endmodule
 
module top;
reg data, clock;
wire q_out, net_1;
  dff inst_1 (.d(data), .q(net_1), .clk(clock));
  dff inst_2 (.clk(clock), .d(net_1), .q(q_out));
endmodule

In the top module there are two instantiations of the 'dff' module. In both cases port connections are done by name, so the port order is insignificant. The first port is input port 'd', the second is output 'q' and the last is the clock in the 'inst_1'. In the dff module the order of ports is different than either of the two instantiations.

Example 2

module dff (clk, d, q);
input clk, d;
output q;
reg q;
always @(posedge clk) q = d;
endmodule
 
module top;
reg data, clock;
wire q_out, net_1;
  dff inst_1 (clock, data, net_1);
  dff inst_2 (clock, net_1, q_out);
endmodule

Example 3

dff inst_1 (clock, , net_1);

Second port is unconnected and has the value Z because it is of the net type.

Example 4

module my_module (a, b, c);
input a, b;
output c;
  assign c = a & b ;
endmodule
 
module top (a, b, c) ;
input [3:0] a, b;
output [3:0] c;
  my_module inst [3:0] (a, b, c);

endmodule 

module DE0_NANO(

input CLOCK_50

);

endmodule

module DE0_NANO(

CLOCK_50

);

input           CLOCK_50;

endmodule