At the ASPA meeting and heard that if a plan has a discretionary P/S contribution it is only allowed to be deposited annually rather than throughout the Plan Year. Is this true and, if so, where can I locate the code siting it. Thanks in advance for any help on this issue.

It is not true, but the plan document needs to have provisions dealing with what happens to the money between the date of deposit and the date of allocation to participant accounts.

IRS Q and A #9 from the 2002 conference:
Q.can you fund discretionary contributions more frequently than annualy, even though your document allocation date is only annual
A. The allocation must follow plan terms

by the way, as a reminder, the Q and A are only opinions, and have not been reviewed or approved by the Service or Treasury.
On the other hand, sometimes they are merely stating the law as is - it is sometimes hard to tell which is which.