Because the PD_ELE_T entry for PD Requests is removed from the PD Send Queue as soon as it is sent, hence for maintaining the last used sequence counter, a list of last sequence counter used per each comId for PD Requests is maintained. The pointer to the first element in the list is added in the TRDP_SESSION struct. Every time a new PD request is to be sent, the last sequence counter used for that comId is fetched from this list.
