Introduction This manual provides a summary and reference to the ST20 architecture and instruction set for the ST20-C1 core. ST20 is a technology for building successful embedded VLSI designs. ST20 devices comprise a collection of VLSI macro-cells connected through a high-performance onchip bus. This architecture allows the easy construction of both general purpose (e.g. ST20-MC1 micro-controller) and application specific devices (e.g. ST20-TPx digital set top box family). ST20-C1 features The ST20-C1 has the following features: • It is implemented as a 2-way superscalar, 3-stage pipeline, with an internal 16- word register cache. This architecture can sustain 4 instructions in progress, with a maximum of 2 instructions completing per cycle. • It uses a variable length instruction coding scheme based on 8-bit units which gives excellent static and dynamic code size. Instructions take between 1 and 8 units to code, with an average of 1.25 units (10 bits) per instruction. • It provides flexible prioritized vectored interrupt capabilities. The worst case interrupt latency is 0.5 microseconds (at 33 Mhz operating frequency). • It provides extensive instruction level support for 16-bit digital signal processing (DSP) algorithms. • It is particularly suitable for low power and battery-powered applications, with low core operating power, and sophisticated power management facilities. • It provides extensive real-time debugging capability through the optional ST20 diagnostic controller unit (DCU) macro-cell, which supports fully non-intrusive breakpoints, watchpoints and code tracing. • It has a flexible and powerful built-in hardware scheduler. This is a light-weight real-time operating system (RTOS) directly implemented in the microcode of the ST20-C1 processor. The hardware scheduler can be customized and provides support for software schedulers. • It provides a built-in user-programmable 32-bit input/output register providing system control and communication capability directly from the CPU.
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