#!/usr/bin/perl
#
# mkboot - generate a bitstream (in .bit format) that boots an M1
#          with the "regular" bitstream, using UrJTAG
#
# Hacked 2001 by Werner Almesberger
#

#
# bitstream file magic, copied from xilinx_bitstream.c:xlx_bitstream_load_bit
#
# here is the source:
# http://urjtag.git.sourceforge.net/git/gitweb.cgi?p=urjtag/urjtag;a=blob_plain;f=urjtag/src/pld/xilinx_bitstream.c;hb=HEAD
#

print pack("C*",
    0x00, 0x09, 0x0f, 0xf0, 0x0f, 0xf0, 0x0f, 0xf0,
    0x0f, 0xf0, 0x00, 0x00, 0x01);

#
# "bitstream" according to Table 7-1 (page 126) of
# http://www.xilinx.com/support/documentation/user_guides/ug380.pdf
#
# and the M1 standby bitstream:
# https://github.com/milkymist/milkymist/blob/master/boards/milkymist-one/standby/standby.v#L205
#
# The 0xffff dummy and the 0x2000 NOP seem to be unnecessary in this case,
# so we omit them.
#
# To boot the rescue bitstream instead of the regular bitstream, change
# the value of GENERAL2 from 0x0037 to 0x0005.
#

@seq = (
#    0xffff,	# DUMMY
    0xaa99, 	# Sync(1)
    0x5566,	# Sync(2)
    0x3261,	# write GENERAL1
    0x0000,	# start address 15:0
    0x3281,	# write GENERAL2
    0x0037,	# start address 23:16
    0x30a1,	# write CMD
    0x000e);	# IPROG
#    0x2000);	# NOP

#
# "e" section in bitstream file, with the length in bytes.
#

print pack("aN", "e", 2*@seq);

#
# the actual bitstream
#

print pack("n*", @seq);