Search for the 2 bytes preceding the jsr 7d98 instruction in a PC Engine rom.

scanJSR7D98.pl

#!/usr/bin/perl -w
use strict;
use File::stat;

die "You must specify a rom name!" unless ($#ARGV == 0);

my $rom = 0;
my $fileSize = stat($ARGV[0])->size;

open(FILE, "<$ARGV[0]") or die $!;
my $nRead = read(FILE, $rom, $fileSize);
close(FILE);

die "Unexpected error!" unless ($nRead == $fileSize);

my $max = 0;
# Find 'byte' in :
# lda byte
# jsr $7d98
while($rom =~ m/(\C)(\C)\x20\x98\x7d/gs)
{
    my ($opcode, $value) = ($1, $2);
    print pos($rom) . " : " . unpack("H*", $value);
    
    my $tmp = unpack("C", $value);
    $max = $tmp if($tmp > $max);
    
    print " !LDA" unless (unpack("C", $opcode) == 0xa9);
    print "\n";
}

printf("Max: %x", $max);