User manual

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Preface
The PDP11 and VAX systems from Digital Equipment Corporation made a major
contribution to the 'boom' of the minicomputer market in the 1980's. Not only provided
these systems cost-effective and modular computing blocks, their open architecture
allowed many third parties to design new interfaces and other product extensions.
Stromasys provides since many years emulators based on the CHARON™ technology,
which accurately represents system hardware by means of software models, so that
unmodified legacy software can continue to be used.
The CHARON-VAX and CHARON-PDP emulators provide complete system emulation,
designed to replace many different PDP11 or VAX hardware systems. Where custom
peripheral hardware is involved, replacement by emulation becomes more complex. Such
systems often remain in place as redesign or emulation is deemed too costly.
For such complex systems, CHARON was developed as an adaptable emulator platform.
In addition to its kernel (with enough functionality to run a basic VAX or PDP-11
configuration), it provides a standard bus interface (the CHARON API: CHAPI). The
CHAPI connects emulated peripherals that are designed as external code modules to the
emulator kernel. Without the need to change the emulator kernel, this allows to modify the
peripheral functionality of the emulated system, as can be required in industrial or process
control systems.
With the CHAPI, custom peripheral hardware can be emulated and connected to the
emulator kernel. With the developer in mind, the CHAPI development wizard has
templates for parallel, serial, disk and tape controllers. The CHAPI library functions
provide the standard elements (registers, interrupt logic, etc) common to all interfaces.
The CHAPI is implemented as a C++ library with the components needed to dynamically
link additional emulated peripheral modules to the core emulator kernel. For third parties
that develop and sell CHAPI modules (which are effectively the emulated equivalents of
hardware peripherals designed for a MicroVAX or PDP-11 system), the CHAPI contains a
product licensing subsystem. The current CHAPI interface definition, libraries and design
information are described in this manual. Source code samples to assist in device
modifications and new design are available on request.
Geneva,14 December 2007.