I couldn't find any examples either, but the important part is the configuration. In 'DIO Config.vi' or 'Digital Group Config.vi', select the input mode as bidirectional.
Their are several Knowledge Base entries that give information on using bidirectional mode. To search the on-line Knowledge Base go to:
www.ni.com >> Technical Documents >> Knowledge Base >> Search all entries
From there you can enter the keywords '8255' and 'bidirectional' to search on.