# d-latch example
#
# A DGD file contains one or more entities.
# Such an entity contains either
#  an import statement
# or 
#  a netlist description.
#
# The import statement allows the inclusion of 
# any other legal file format for dgc.
# Port names are taken from the imported file.

# In this example the file d_latch.bex has the
# input ports 
#   e  enable data
#   d  data input
# and the output 
#   r  output for the reset input of a rs-latch
#   s  output for the set input of a rs-latch
entity d_latch_logic
{
  import "/usr/share/dgc/d_latch.bex";
}

# Additionaly the import statement might be changed
# by one or more option statements. Options are similar
# to the commandline options of DGC. In this case the
# finite state machine is created without flip-flops (async)
# and without a reset line (nrs).
# There can be one or more space separated options for one 
# option statement.
#
# The rs-latch has the inputs 'r' and 's' and one output port 'q'
entity rs_latch
{
  option async nrs fbo;
  import "/usr/share/dgc/rs_latch.kiss";
}

# An entity can contain a netlist instead of the 
# import statement.
# A netlist requries:
#  - One or more port statements to describe the 
#    input and output lines. Syntax is:
#    'port' ('input'|'output') {<portname>}
#  - Some 'use' statements. The first argument of the 
#    'use' statement is the name of a previously 
#    defined entity. All following names represent the 
#    name of the included subcircuits. Syntax is:
#    'use' <entityname> {<componentname>}
#  - Several 'join' statements. A 'join' statements 
#    connects two or more ports together. If the same
#    port is used in two different join statements, 
#    all ports of the two 'join' statements are connected.
#    For example
#      join a:x b:y;
#      join a:x c:z;
#    is the same as
#      join a:x b:y c:z;
#    The syntax for the 'join' statement is:
#      'join' {<componentname>':'<portname>}
entity d_latch
{
  port input d e;
  port output q;
  use d_latch_logic l;
  use rs_latch rs;
  join l:d d;
  join l:e e;
  join l:r rs:r;
  join l:s rs:s;
  join rs:q q;  
}