Commercially available behavioral synthesis tools do not adequately support FPGA vendor-specific external memory interfaces making it extremely difficult to exploit pipelined memory access modes as well as application specific memory operations scheduling critical for high-performance solutions. This lack of support substantially increases the complexity and the burden on designers in the mapping of applications to FPGA-based computing engines. In this paper we address the problem of external memory interfacing and aggressive scheduling of memory operations by proposing a decoupled architecture with two components - one component captures the specific target architecture timing while the other component uses application specific memory access pattern information. Our results support the claim that it is possible to exploit application specific information and integrate that knowledge into custom schedulers that mix pipelined and non-pipelined access modes aimed at reducing the overhead associated with external memory accesses. The results also reveal that the additional design complexity of the scheduler, and its impact in the overall design is minimal.