Kernel Products


smx86™

The 32fpm version of smx86 provides 32-bit protected mode support, without segmentation. Many users prefer flat-mode addressing, because it is simpler. This is the only 32-bit mode supported by the Microsoft and Borland 32-bit x86 compilers. In this mode, the segment registers are loaded only once, during startup. Assembly language portions of smx86 have been rewritten to take advantage of 32-bit instructions and to remove segmentation.

The services provided by smx86 for 32fpm are the same as for rm and for 16spm, except for the omission of the far heap, far stacks, and other far objects. A single flat-model smx library is provided. When smxSim is also purchased (see below), a special version of the smx library is provided that is suitable for execution of the Protosystem/application in a Win32 environment.

An smx86 32fpm application can be built as an OMF, HEX, or BIN file using a linker/locator or built as an EXE (PE format) to run under pmEasy32. Linker/locator support includes startup code and a build script for the Protosystem. These can be used for the application, with very little change. Startup code copies descriptor tables and initialized variables from ROM to RAM. It also offers the option to start from the reset vector or to start as a BIOS extension. Paradigm C++ is supported for building located code. Microsoft and Borland 32-bit tools and the Embedded Power Link & Locate 386 and Visual Probe are also supported for building located code. Microsoft and Borland 32-bit tools and the Soft-Scope debugger are supported for building an EXE. smxSim is for use with EXE builds to allow them to run in a Win32 environment.

For more information on picking the best version of smx86, for your project, see our whitepaper Choosing an smx86 Version.

Additional x86 Features

Stack Flexibility

In addition to the stack flexibility provided by all versions of smx, segmented smx86 allows stacks to be allocated from either the near heap or the far heap on a task-by-task basis. Thus, a task requiring a near stack, so that ss == ds, can get its stack from the near heap. However, since the near heap is very small, this is possible only for small stacks. For other tasks, stacks of up to almost 64KB can be allocated from the far heap. For compact and large memory modules, the stack pool is in its own segment, allowing up to 64KB of stack pool space and conserving precious space in near memory. In this case, ss != ds, which is ok for smx (but may not be for all application code).

Coprocessor State Saving

For a task using the x87 coprocessor, smx86 will automatically save the coprocessor registers when the task is suspended and restore coprocessor registers when the task is resumed. The coprocessor's state is saved only for tasks that use it - and only in sections of the task that use it, if desired. This way, tasks not using the coprocessor are not burdened with this extra overhead (which is significant).

DOS Support

Although smx86 was designed as a ROM'able kernel, the real-mode version will run with DOS. The smx DOS Protosystem provides code to trap DOS calls so that only one task, at a time, may perform a DOS call. If a higher priority task attempts a simultaneous DOS call, it is automatically suspended on the in_dos semaphore until the current task completes its DOS call. The DOS Protosystem also inhibits smx stack checking when in a DOS call because DOS switches stacks. It exits cleanly back to DOS, when the application is terminated.

Hand-tuned Scheduler

The smx86 scheduler is written in x86 assembly language and is hand-tuned for optimal performance, using many advanced x86 techniques.

PC Operation

smx86 includes a Board Support Package (BSP) for operation on standard PC's. This includes most PC-clone boards (e.g. PC104). The smx86 BSP includes a keyboard handler, direct screen write functions, 16550 UART driver, and tick handler. Normally, the BIOS provides board initialization.

x86 Support Products

smx86 is supported by a wealth of other Micro Digital products. What follows is a brief description of each. For more information, see corresponding brochures and manuals.

smxProbe

smxProbe permits task-level debugging. It allows the user to display control blocks, queues, and trace buffers, symbolically for all symbols entered into the smx handle table. It keeps trace information for tasks, smx calls, and smx errors. Sophisticated stop-trace points may be set. smxProbe uses the target's keyboard and display. If the target does not have these, smxProbe may be operated from a remote terminal via a cable connected to a serial port on the target. smxProbe will also operate with debuggers such as Turbo Debugger and CodeView to inspect smx objects while stopped at a breakpoint. smxProbe is now included with smx86 at no additional charge.

smxAware for Paradigm C++, VisualProbe, and Soft-Scope

smxAware is a DLL that is loaded by the host debugger thereby, adding smx awareness. This permits viewing smx objects and queues symbolically by selecting the smx pull-down menu. smx objects may also be placed in a watch window, and task-aware breakpoints may be set.

smxWindows

smxWindows is a text-based windowing package. It is a step beyond the simple direct screen write functions provided with smx. It contains 25 calls for functions such as creating a window, displaying a pop-up window, accepting a menu selection, moving a window to the top of the of the stack or to the bottom, displaying a string of characters or a character, entering keyboard input into a window, setting the cursor position, clearing or scrolling a window, and other operations. The package requires only 10.5KB, max. It works with standard PC monitors and keyboards. Full source code is provided to permit modifying smxWindows for use with other hardware. smxWindows is now included with smx86 at no additional charge.

Bootloader and unDOS

The Real Mode EXE Bootloader is capable of loading and executing a real-mode, EXE file from boot, without DOS present. It relies only on BIOS services. This saves the cost of DOS royalties and frees additional memory for the application. Virtually the entire RAM below 1MB is available to the application, since the space occupied by the loader becomes available, once the load has completed.

If the application makes int 21h DOS calls or certain BIOS calls, unDOS may be used to emulate those calls. This may permit a DOS application to considerably extend its memory above the 640K limit of DOS.

pmEasy and unDOS

pmEasy is used for protected mode EXE applications. It will bootload from the BIOS or can be loaded via DOS. It switches the processor from real-mode to protected-mode and loads the protected-mode application from one of several possible storage devices. pmEasy also provides services to perform protected mode operations such as memory allocation, hooking interrupts, creating descriptors, etc. These services are DPMI-compatible. (The DOS Protected Mode Interface is a standard developed by Intel, Microsoft, and others for protected-mode services.)

If loaded by DOS, pmEasy exits cleanly back to DOS when the application is terminated. This is convenient for running DOS utilities after the application performs its function.

If the application makes int 21h DOS calls or certain BIOS calls, unDOS may be used to emulate those calls. Thus, pmEasy with unDOS provides an alternative to using a DOS extender. pmEasy with unDOS is simpler than a DOS extender and it provides much better performance. This is because pmEasy was designed for real-time embedded systems, whereas DOS extenders were intended for desktop systems.

unWin

unWin includes unDOS and provides some Win32 emulation for 32fpm applications.

smxSim

smxSim permits running 32fpm smx applications under Windows 9x and NT. The application can be developed and debugged under Microsoft Visual Studio or the Borland IDE. This ability to run on the host is convenient since it avoids waiting for code to download to the target and avoids concerns about hardware startup code. It also allows getting started before the target hardware is available. When running in the IDE or directly on Win 9x or NT the application linked with smx runs as a Windows app. As such, it is subject to limitations imposed by Windows.

smxSim, which is inexpensive, has been used in many projects to reduce debugger expense. It is adequate for task and GUI code development seats. Thus, only a few seats of expensive debuggers may be necessary for BSP and integration work.

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