vhdl_printf

This vhdl package implements printf for vhdl. It allows you to do formatted printing to a LINE type.

Installation

To install PCK_FIO, define a VHDL library called EASICS_PACKAGES, and analyze the VHDL file PCK_FIO_1993.vhd and PCK_FIO_1993_BODY.vhd into this library.

Modelsim

vlib easics_packages
vcom -work easics_packages PCK_FIO_1993.vhd PCK_FIO_1993_BODY.vhd TB_PCK_FIO_1993.vhd
vsim -do "run -all" TBE_PCK_FIO
diff PCK_FIO.out.gold PCK_FIO.out

ghdl

mkdir easics_packages
ghdl -a --std=93 -Peasics_packages --work=easics_packages --workdir=easics_packages PCK_FIO_1993.vhd PCK_FIO_1993_BODY.vhd TB_PCK_FIO_1993.vhd
ghdl -e -Peasics_packages --work=easics_packages --workdir=easics_packages TBE_PCK_FIO
./tbe_pck_fio
diff PCK_FIO.out.gold PCK_FIO.out

Usage

PCK_FIO is a VHDL package that defines fprint, a function for formatted file output.

After installing the package you can call fprint as follows:

  fprint(F, L, Format, fo(Expr_1), fo(Expr_2), ... fo(Expr_n));

where F is the filehandle and L is the line variable.

The argument Format is the format string, which consists of ``normal'' substrings which are copied verbatim, and format specifiers, starting with '%'. A typical format string looks as follows:

   "Arg1 = %6r, Arg2 = %10d, Arg3 = %-5r\n"

The remaining arguments are the expressions whose results you want to write to the file, embedded in fo function calls. There can be 0 to 32 of such arguments. The expressions can be of any type for which an fo function exists. String expressions can also be called directly.

The file output function 'fo'

The fo (file output) functions do the trick. They return a tagged string representation that is meaningful to format specifiers. Here are some examples:

  fo (signed'("1100"))   returns "S:1100" 
  fo (unsigned'("1100")) returns "U:1100" 
  fo (TRUE)              returns "L:T"
  fo (127)               returns "I:127"

The internal behavior of fo is irrelevant to the typical user.

The fo function is currently overloaded as follows:

  function fo (Arg: unsigned)          return string;
  function fo (Arg: signed)            return string;
  function fo (Arg: std_logic_vector)  return string;
  function fo (Arg: std_ulogic_vector) return string;
  function fo (Arg: bit_vector)        return string;
  function fo (Arg: integer)           return string;
  function fo (Arg: std_ulogic)        return string;
  function fo (Arg: bit)               return string;
  function fo (Arg: boolean)           return string; 
  function fo (Arg: character)         return string;
  function fo (Arg: string)            return string;
  function fo (Arg: time)              return string;

To support null-terminated strings, the function fo(Arg: string) processes Arg up to the first NUL character, if any. If you want the whole string to be outputted you can just enter the string as a direct argument in fprint. See also the examples in the testbench.

###Format specifiers

The general format of a format specifier is:

   %[-][n]c

The optional - sign specifies left justified output; default is right justified. The optional number n specifies a field-width. If it is not specified, fprint does something reasonable.

c	is the conversion specifier. Currently the following conversion specifiers are supported
r	reasonable output format (inspired by Synopsys VSS) Prints the ``most reasonable'' representation e.g. hex for unsigned, signed and other bit-like vectors (not preferred for integers)
b	bit-oriented output
d	decimal output
s	string output (e.g. in combination with 'IMAGE for enum types)
q	``qualified'' string output (shows internal representation from fo)
{}	Iteration operator, used as follows: %n{} In this case, n is the iteration count and is mandatory. Iteration can be nested.

Special characters

To print a double quote, use '""' in the format string (VHDL convention). To print the special characters, '', and '%', escape them with ''. To prevent '{' and '}' from being interpreted as opening and closing brackets in iteration strings, escape them with ''.

A newline is specified in the format string by '\n'.

History

This was an open source package developed by easics.com in 2001. The only think I have done is created a repo on github and uploaded it. I did reformat this README file and added a license file. Below is the original readme file: