This variable can be used to turn timing output on and off at specified times. While print-timing is asserted, a line is output along with all the chat messages since the last line was printed. A line is printed only when if it is different from the last line printed. Each of the signals can a literal string or character, or a scheme expression.
Literal characters appear on each line of the timing diagram and are used as visual separators.
A literal string is used to give name to the expression which immediately follows it in signals . Every 50 cycles of printed output, a header composed of the expression names is printed with the names rotated 90 degrees. Long expressions without preceeding strings can make for awkward looking output. While print-timing is asserted, each scheme expression is evaluated every cycle, and its value printed in the order of signals . Numeric values are printed as two-digit hexadecimal numbers.