ROMless MCUs for Real-Time Control

SGS-THOMSON Microelectronics has extended its ST10 family of 16-bit microcontrollers with the introduction of the ST10R163 and ST10R165 ROMless devices. Both offer very fast responses to internal or external service requests and are particularly suitable for real-time control applications, where there is a high software content, such as ISDN telephone systems, point of sale terminals and bank autotelling machines.

The ST10 family is based around a high performance 10 MIPS CPU core featuring a four-stage pipeline and 500ns multiplication time. The CPU employs a register-based architecture with the registers implemented as windows on a 1k byte block of very fast internal SRAM. This means that the high speed context switches required to meet the multi-tasking and fast interrupt requirements of real-time embedded applications can be performed simply by exchanging a register pointer. In this way, the ST10 achieves maximum interrupt response times of less than 1us.

To minimize CPU overheads, ST10 devices allow data transfers between peripherals and memory to be optionally handled using a cycle stealing technique instead of conventional interrupt service routines. This is achieved by means of an eight-channel Peripheral Event Controller (PEC), which is essentially a programmable multi-channel data movement engine that complements the on-chip Interrupt Controller.

Interval timing and pulse/frequency generation are two of the most important functions required in embedded control applications and the new devices include five independent 16-bit timers that can be programmed to perform all the popular pulse measurement and generation functions without requiring any external logic. Similarly, the integrated 8/16-bit External Bus Controller eliminates the need for external memory interface logic and allows the overall system to be optimized for highest performance or lowest cost.

Because today's embedded systems are typically developed using stack-based high level languages such as C++, the ST10R163 and ST10R165 include comprehensive support for stack operations. These include not only a full set of instructions for stack manipulation but also mechanisms that allow stack overflow and underflow to be detected and safely handled.

With 2k bytes of on-chip RAM, the ST10R165 is a pin-compatible replacement for the Siemens C165-LF device; the ST10R163 has 1k byte of on-chip RAM, a watchdog oscillator and a phase-locked loop (PLL) circuit. Other devices in the ST10 family include the popular ST10F166 which contains 32Kbytes of on-chip flash memory.

February 1997

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