Allow the user to specify the JTAG ID

[sgherbst]

The tap template allows the user to specify version[3:0] (valid range 0 through 15), part[15:0] (valid range 0 through 65535), and man_num[10:0] (valid range 0 through 2047):

JusTAG/justag/rtl/digital/tap.svp

Lines 170 to 172 in a28512f

	.version(`$version`),
	.part(`$part`),
	.man_num(`$man_num`),

These are taken together to form the JTAG ID (note that the LSB is always "1")

logic [31:0] id_code = {version, part, man_num, 1'b1};

It would be great it the user could optionally specify these parameters. This would allow them to do things like encode the git commit hash in the ID for debugging purposes. This feature could be exposed as optional command-line arguments (something like justag --version NNNN --part NNNN --man_num NNNN file1 file2 ...).

Right now, it might be a little cumbersome to add these command-line options because sys.argv is read directly:

JusTAG/justag/JusTAG.py

Line 49 in a28512f

list_of_files = sys.argv[1:]

However I think if this is changed to an ArgumentParser-based approach, it should be relatively quick. By the way, please validate the user input for these three arguments to ensure that they fall within the allowed range of values. Thanks!

[sgherbst]

Please see updated comments since there were some errors in my understanding of the tap template.