CAMBRIDGE, UK, May 23, 2000, Crossware (, a leading embedded software tools developer, has announced a new version of its 8051 Virtual Workshop which supports multi-processor systems. Programmers will now be able to debug and verify software for multi-processor systems in the absence of any target hardware thereby reducing software development timescales significantly.

The new 8051 Virtual Workshop supports the automatic address recognition protocols provided by the Universal Asynchronous Receiver Transmitters (UART) of a number of 8051 variants including the Dallas range of High Speed Micros such as the DS87C320 and some of the Philips variants such as the PS8XC51FX series of chips. When the Crossware 8051 Virtual Workshop is set up to simulate one of these variants, it will automatically support its automatic address recognition protocol.

This automatic address recognition allows serial communication between microcontrollers to occur with a minimum of processor intervention. By running multiple instances of the Virtual Workshop, either on a single PC or multiple PCs connected together on a network, multiple target systems can be simultaneously simulated. These virtual target systems can then communicate with each other using the Virtual Workshop’s extension interface allowing the target software to be fully developed without hardware.

The 8051 microcontroller has always supported multi-processor communication. By switching the UART to a special mode, it can be prevented from interrupting the microcontroller unless a special bit of the received data is set. The microcontroller then knows that if it is interrupted, the data represents an address. It can then examine this address to see if it matches its own and, if it does, switch itself into a different mode in which it will receive subsequent data.

More recent 8051 variants have extended this multi-processor support by building the address recognition into the hardware of the chip. The microcontroller need then only be interrupted if the received data matches the address programmed into the microcontroller. A mask byte

can also be programmed into the microcontroller allowing it to receive data being broadcast to multiple addresses.

Products that might exploit this feature include data terminals which receive updates from a central control system, sensor systems which are interrogated by a monitoring station and multi-axis robots with each axis under the control of its own processor.

To simulate multi-processor communications a Virtual Workshop custom extension will send the output to and receive input from other target systems. If other target systems are also being simulated in other instances of the Virtual Workshop, then data can be transferred between them using a Windows inter-process communication method such as mailslots, named pipes or sockets.

The Virtual Workshop can also communicate with a real target system. The I/O of the simulating UART can be sent to and received from the real serial port of the PC which can in turn be connected to an actual target board.

The 8051 Virtual Workshop runs under Windows 95, Windows 98 and Windows NT4.0. At the heart of the system is an 8051 Instruction Set Simulator with full source level and graphical debugging facilities. What turns this simulator into a Workshop is the fact that it can rapidly be extended into a total simulation of the target system.

Integrated seamlessly with the Crossware Embedded Development Studio which provides project management, editing and other advanced facilities, the 8051 Virtual Workshop works extremely effectively with the 8051 ANSI C compilers and assemblers from Crossware but it works equally well stand-alone, with tool chains from other vendors.


About Crossware (

Crossware is a leading developer of programmer-friendly C cross compilers and other development tools for embedded systems based on the 8051, ColdFire, 68000, CPU32 and other chip families. Host environments include Windows NT, Windows 98, Windows 95 and DOS. The company, founded by Alan Harry in 1984, is headquartered in the UK at Litlington on the outskirts of Cambridge. Crossware’s products are used throughout the world by professional developers, educational establishments and hobbyists.