Supervisory Control and Data Acquisition (SCADA) systems are traditionally proprietary and well protected. Due to increasing use of commercial/open source technology and communication protocols, there are growing concerns about the associated security threats. SCADA networks are usually employed in critical infrastructure, therefore, not much technical data of the actual systems is accessible to the research community.Most of the researchers simulate the SCADA functioning through development of testbed. Such projects are usually expensive and requiring financial sponsorship. In this paper we present a simple, inexpensive and flexible approach to develop a SCADA testbed utilizing TrueTime, a MATLAB/ Simulink based tool. The paper describes TrueTime simulation blocks, our control system, simulation of Denial of Service (DoS) attack and its effects. The main aim was to assess the effectiveness and suitability of TrueTime for the intended use in the development of a larger scale SCADA testbed. The results shown reflect that TrueTime can be effectively used for the purpose of SCADA network simulations and collection of necessary data for security analysis.