System design kit for the 8051

Abstract

A tiny real-time dataflow operating system kernel has been developed, named TERSE (Tiny Embedded Real-time Software Environment), initially for the 8051 series of microcontrollers, and version “G” is released into the public domain. Most embedded applications development, using small conventional-architecture single-chip microcontrollers, is done without an underlying software kernel, however the advantages of an operating system can be realised even at this low level. TERSE does not use the usual time-slicing/preemption of small RTOSs (Real-Time Operating Systems), but instead employs a cooperative dataflow model. The advantages seen, are modularity, easy parallelism, transparent distributed processing, a high level of determinism, object orientation, and timing enhancements for 1/O and real-time applications. Signature Scheduling, a combination of static and runtime scheduling, provides deterministic behaviour with the flexibility required of a reactive real-time system. It is also anticipated that there will be advantages in terms of reduced development time, in particular the meshing with high-level DFD/STD (Data Flow Diagram/State Transition Diagram) design tools, and easier maintenance, and a complementary flow-diagramming technique called tFlow has been developed. Also, TERSE is extremely easy to use, fast, and compact. The memory requirement of version G for the 8051, is about 420 bytes of ROM, including network interfacing, and the uniprocessor version is only 150 bytes.