This paper addresses a high-level synthesis (HLS) using dual-edge-triggered flip-flops (DETFFs) as memory elements. In DETFF-based HLS, the duty cycle becomes a manageable resource to improve the timing performance. To utilize the duty cycle radically, a programmable duty cycle (PDC) mechanism is built into this HLS, and captured by a new HLS task named PDC scheduling. As a first step toward DETFF-based HLS with PDC, the execution time minimization problem is formulated for given results of operation scheduling. A linear program is presented to solve this problem in polynomial time. As a next step, simultaneous operation scheduling and PDC scheduling problem for the same objective is tackled. A mixed integer linear programming-based (MILP) approach is presented to solve this problem. The experimental results show that the MILP can reduce the execution time for several benchmarks.