User manual

2.CHAPI programming concepts

2.1 Overview

The CHAPI interface provides the ability to load dynamically (at run-time, during the

configuration phase) additional emulator components that implement customer specific

devices (for QBUS and UNIBUS in the version discussed in this release). The CHAPI

architecture defines a programming interface of communication between such a loadable

component and the core of CHARON. This interface must contain the following elements:

• Inform the loadable component when it is necessary to create, initialize, terminate, and

destroy instances of a device.

• Provide a means of configuring instances of a device as specified in the emulated

system configuration.

• Deliver bus signals (such as BUS RESET, IRQ ACKNOWLEDGE) to instances of a

device.

• Provide access of the emulated CPU to device control/status registers for each

instance of device.

• Deliver bus requests (interrupt requests) on behalf of an instance of a device.

• Provide a means of reading/writing memory for DMA capable devices.

• Provide a means of license verification in order to protect the loadable component from

uncontrolled distribution.

• Provide a means of message logging coordinated with message logging of the

CHARON itself.

To meet the above needs the loadable components are implemented as .DLL modules in

the Windows host platform of CHARON. They define a set of procedures, data structures,

and behaviors that allow the core of CHARON and the loadable component to

communicate as required.

2.2 Loadable component naming conventions

Each loadable component must have a name, typically assigned by the developer of the

component. This name must be sufficiently unique to allow users to identify the

component. As far as the loadable component usually represents a class of peripheral

devices, it is recommended to derive the name of the loadable component from the name

of the device class.