SystemVerilog Language

2-State Data Types

bit [msb:lsb] var_name [=initial_value];
default : 0
x or z 값은 0으로

• byte : 8 bit signed
• shortint : 16 bit signed
• int : 32 bit signed
• logint : 64 bit signed

• reale : double in C
• shortreal : float in C
• realtime : 64 bit 실수, $realtime 으로 사용

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4-State Data Types

reg | logic [msb:lsb] variable_name [=initial_value];
default : x

• integer variable_name [=initial_value]; : 32 bit signed
• time variable_name [=initial_value]; : 64 bit unsigned
  "ns" 같은 time unit 사용 가능

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String Data Type

string variable_name [=initial_value]

• default : ""
• $sformat() 시스템 함수로 생성 가능
• ==, !=, compare(), incompare()
• itoa(), atoi(), atohex(), toupper(), tolower()
• len(), getc(), putc(), substr() 등 사용 가능

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Enumerated Data Types

• Define
  typedef enum [data_type] {named constants} enumtype

• Declare
  enumtype var_name [=initial_value]

default : int 형, '0
name() 함수나 %p 로 ASCII 코드 출력 가능

typedef enum bit[2:0] {IDLE=1, TEST, START} state_e;
state_e current, next = IDLE
$display("current = %0d, next = %s", current, next.name());
$display("next = %p", next);

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Data Arrays

Fixed-size Arrays

type array_name[size] [=initial_value]

int b[2] = '{3, 7};

bit[31:0] c[2][3] = '{{3,7,1},{1,2,3}};
byte d[7][2] = '{default:-1};

bit [31:0] a[2][3] = c;  // types and sizes must be same
for(int i=0; i<$dimensions(a), i++;)
  $display($size(a, i+1));  // 2 3 32 출력

Dynamic Arrays

type array_name[] [=initial_value];

logic[7:0] ID[], array[] = new[16];
logic[7:0] data_array[];

ID = new[100];
data_array = new[ID.size()] (ID);  // copy - types muast match

ID = new[ID.size() *2] (ID);
data_array.delete();

Queues

type array_name[$[:bound]] [=initial_value];

• push_back(), push_front(), insert()
• pop_back(), pop_front(), delete() 등
• new[16]; 사용 안됨

int j = 2;
int q[$] = {0,1,3,6};
int b[$] = {4,5};
q.insert(2, j);  // {0, 2, 3, 6}
q.insert(4, b);  // {0, 1, 2, 3, 4, 5, 6}
q.delete(1);     // {0, 2, 3, 4, 5, 6}
$display("%p", q); // '{0,2,3,4,5,6}

Associative Arrays

type array_name[index_type];

• first(), next(), prev(), last()
• num()
• exists()

byte opcode[string], t[int], ID_aray[bit[15:0]];
int index;

opcode["ADD"] = -8;
for (int i = 0; i < 10; i++)
  t[1<<i] = i;

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Loop Support and Reduction Oprators

int data[] = '{1,2,3,4,5,6,7}, qd[$][];
qd.push_back(data);
foreach(data[i])
  $display("data[%0d] = %0d", i, data[i]);
  
$display("sum of array content = %0d", data.sum());
$display("product value is = %0d",     data.product());
$display("and'ed value is = %0d",      data.and());
$display("or'ed value is = %0d",       data.or());
$display("xor'ed value is = %0d",      data.xor());

Array Methods

• find(), find_index()

program automatic test;
  bit[7:0] SQ_array[$] = {2, 1, 8, 3, 5};
  bit[7:0] SQ[$];
  int idx[$];
  
  initial begin
    SQ = SQ_array.find() with ( item > 3 );  // item is default iterator variable
  
    idx = SQ_aray.find_index(addr) with ( addr > 3 );
  end
endprogram: test

• find_first(), find_first_index()

program automatic test;
  int array[] = new[5];
  int idx[#], val[$], dyn_2d[][], mixed_2d[$][];
  
  initial begin
    foreach(array[i])
      array[i] = 4 - i;
    
    val = array.find_first() with ( item > 3 );  // val[0] == 4
    idx = array.find_first_index() with ( item < 0 ); // idx == {}
  end
endprogram: test

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Unpacked Array Performance

Array Type	Application	Performance
Fixed-Size	Use in RTL for FIFO, Memory, Buffer.	Best
Dynamic	Random read/write access 필요할 때	Good
Queue	Stack, CAM applications, Scoreboard	Good
Associated	sparse memory applications 에 유용함. hash tables 만들 때 사용	Moderate

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Packed Array

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Out-of-Bounds Access

int addr[$:4] = {0,1,2,3,4};
addr.push_back(10);
addr[0] = addr[5];

error 발생 안하지만 push_back해도 안되고
addr[5]는 0을 반환

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Randomization

$urandom : Return 32 bit unsigned random number
$urandom_range(max, [min]) : Return 32 bit unsigned random number in specified range. min 의 default는 0
randcase : Select a weighted executable statement

randcase
  10 : f1();
  20 : f2();
  50 : x = 100;
  30 : randcase ... endcase;
endcase

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User Defined Types

typedef bit [31:0] uint; // define
uint my_var;             // create variable

bit[7:0] payload[];

int temp = $urandom;
payload = new[(temp % 3) + 2];
payload = new[(uint'(temp) % 3) + 2];

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Operator

inside

bit [31:0] r1, r2, smpl;
int golden[$] = {3,4,5};

if (smpl inside {[r1:r2]}) ...
if (result inside {1, 2, golden}) ...

x, z는 무시됨
integral expressions 에서는 wildcards(==?) 사용됨

iff

몰라

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Subroutine(task and function)

task는 block 가능, function은 불가능

direction	effect
input	copy value in at beginning - default
output	copy value out at end
inout	copy in at beginning and copy out at return
ref	pass by reference
const ref	pass by reference but read only

default direction : input
default type : logic

Helpful Debugging Features

function void check();
  static int cnt = 0;
  string message;
  if (!compare(message)) begin
    $display(%m\n[ERROR]%t: %s", $realtime, message);
    $finish;
  end
  $display("[NOTE]%t: %0d Packets passed\n", $realtime, ++cnt);
endfunction: check