This paper is concerned with the development of software for real-time, safety-related embedded systems. The particular focus of the paper is on ‘Time-Triggered’ (TT) systems. TT design can be viewed as a subset of more generic ‘Event Triggered’ (ET) designs. When compared with ET alternatives, TT designs have a simple software architecture and – once constructed – are generally accepted as being easier to test. As a consequence, forms of TT design have been used for many years in industries such as aerospace, because they have been found to provide the basis for safe and reliable systems. Despite the growing demand for safety-related embedded systems in sectors such as industrial control, automotive and household goods, use of TT architectures is less common than ET architectures in these areas. This paper explores some of the benefits of modern TT designs, and considers some of the reasons why this approach is less commonly used than ET architectures in current safety-related designs.