Standard Package |
LRM §14.2. |
The Standard package predefines a number of types, subtypes, and functions.
The Standard package is part of the VHDL standard. This package contains definitions for basic types, subtypes, and functions, and the operators available for each of the (sub)types defined.
Use of the Standard package is implicitly assumed by every VHDL simulator and compiler and need not to be explicitly declared by the use clause.
package standard is
type boolean is (false,true);
type bit is ('0', '1');
type character is (
nul, soh, stx, etx, eot, enq, ack, bel,
bs, ht, lf, vt, ff, cr, so, si,
dle, dc1, dc2, dc3, dc4, nak, syn, etb,
can, em, sub, esc, fsp, gsp, rsp, usp,
' ', '!', '"', '#', '$', '%', '&', ''',
'(', ')', '*', '+', ',', '-', '.', '/',
'0', '1', '2', '3', '4', '5', '6', '7',
'8', '9', ':', ';', '<', '=', '>', '?',
'@', 'A', 'B', 'C', 'D', 'E', 'F', 'G',
'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O',
'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W',
'X', 'Y', 'Z', '[', '\', ']', '^', '_',
'`', 'a', 'b', 'c', 'd', 'e', 'f', 'g',
'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o',
'p', 'q', 'r', 's', 't', 'u', 'v', 'w',
'x', 'y', 'z', '{', '|', '}', '~', del);
-- VHDL'93 includes all 256 ASCII characters
type severity_level is (note, warning, error, failure);
type integer is range -2147483647 to 2147483647;
type real is range -1.0E308 to 1.0E308;
type time is range -2147483647 to 2147483647
units
fs;
ps = 1000 fs;
ns = 1000 ps;
us = 1000 ns;
ms = 1000 us;
sec = 1000 ms;
min = 60 sec;
hr = 60 min;
end units;
subtype delay_length is time range 0 fs to time'high;
impure function now return delay_length;
function now return time; -- VHDL'87 only
subtype natural is integer range 0 to integer'high;
subtype positive is integer range 1 to integer'high;
type string is array (positive range <>) of character;
type bit_vector is array (natural range <>) of bit;
type file_open_kind is (
read_mode,
write_mode,
append_mode);
type file_open_status is (
open_ok,
status_error,
name_error,
mode_error);
attribute foreign: string;
end standard;