Frequently Asked Questions (supposidly)

Ver 1.3

Modification History:

1.01: Initial version indicated substantial performance drop when using LPT port over 8255 PIO. Latest prototype LPT drivers now offer similar performance to PIO so removed these references.

1.1: Update for Windows V3.0 release.

1.2: Update for Windows V3.1 release.

1.21 Include link for US 8255 IO card source

1.3: Update for Windows V4.0 release.

1. What is PC-Share?

At it's most abstract, PC-Share is an executable program which provides control over a number of PC peripherals from another computer. The remote computer talks to PC-Share via a hardware port using a message based protocol.

There are a number of different PC-Share programs available for download on this page, and full descriptions of their capabilities are given with each one. The latest version (4) is a Windows only program (both 16 bit & 32 bit), however the previous version (3.2) is still available for download on MS-DOS and Windows platforms. Whether you use a Windows or DOS version they all offer the same key features:

2. What hardware is needed for PC-Share?

The remote computer needs a physical hardware link to the PC. In practice, this should be as fast as possible therefore parallel is preferable over serial. PC-Share does not contain any sort of data packaging or error detecting which would be required for a serial link and no drivers exist for it at the moment. However, this may not be the case in the future if serial support is desired.

3. Which hardware interface's does PC-Share support?

PC-Share is shipped with two sets of parallel port drivers. The first utilises an Intel 8255 PIO. This is a dedicated parallel port chip which is not part of a standard PC's architecture. In order to use this chip you will need to add a dedicated card to your PC's ISA bus - one such card is available in kit form from Maplin Electronics in the UK for about £25.

The scond driver uses the standard printer (LPT) port. In order to be able to use this driver, your parallel port must be one of the newer variants which supports 'byte mode' reverse data transfer.

To switch between each one simply involves (for the Windows versions) selecting the required DLL or (for the MS-DOS version) using the correct executable.

4. How to I develop or use a different driver with PC-Share

Both DOS and Windows development kits are available along with sample driver code for the 8255 chip. In the case of the DOS version, you will need a Borland C compiler to write and build in your new driver.

The Windows version requires access to a compiler which can build DLLs - the new driver is written in the form of a DLL which then replaces the one shipped with PC-Share.

5. What else is required to run PC-Share?

Firstly, the remote computer which you intend will be utilising PC-Share. A hardware interface which is capable of connecting to your designated hardware interface on the PC. And finally software drivers which can talk and control the PC-Share interface through it's message based protocol.

If your remote computer does not have an interface which can connect to the PC, you will need to build one for it. Then you will need to write the software required to talk to the interface and communicate with PC-Share. This can take the form of device drivers for your operating system (ideally) or programs which you run, to say copy an MS-DOS file.

6. Do any drivers/computers exist which use PC-Share?

Yes. At it's outset PC-Share was written to be driven by a computer running the OS9 operating system. Device drivers and file managers exist to fully interface to PC-Share from a computer running 6809/OS9. In particular, OS9 Level 1 on a Dragon computer. The drivers are downloadable from this page along with some source files to allow development for a different OS or IO chip.

7. How do the OS9 drivers interface to PC-Share?

The OS9 drivers are based around the Motorola MC6821 PIA which is a dedicated parallel port driver chip. The drivers allow for the chip to be mapped anywhere within the machine's address map with only minor modifications needed to the device descriptors. For optimum performance, an 8 bit parallel link is used to connect to the 8255 PIO (or printer port) in the PC.

The OS9 driver set forms part of the operating system, such that the PC's disk drives and devices can be referenced as an actual OS9 device, so files can be copied and moved around using standard operating system commands (such as copy,dir,list etc.).

8. What modifications are required to a Dragon to support PC-Share?

At present, a new MC6821 PIA needs to be added. This involves some work on the Dragon, requiring new IO spaces to be decoded and extra circuitry to be added.

However, a new driver set may be available soon which makes use of the existing centronics printer port on the Dragon with only a few minor hardware modifications. All that remains is for a dedicated cable to be made up.

9. What do I do now if.......

I need to understand the hardware needed by my computer for PC-Share?

Get the parallel comms document. This talks about MC6821's but the jist is there. Your port needs to be capable of performing this sort of transfer. For best performance, many chips support auto-strobing (like the 6821 and i8255) where as you read/write a byte the control line handshaking is handled by the hardware. Where the performance may drop slightly is when you have to do the handshake in software (as in the PC's LPT port or Dragon's printer port). However, it is unlikely to have a significant impact on data throughput.

I'm not using a Dragon/6809 based machine and need to build some hardware?

This is beyond the scope of my pages. For each computer it's going to be different and you'll need a good understanding of the hardware involved and some basic interfacing techniques. However, for some basic address decoding material you can check out the address decoding Up2Date article for the Dragon.

I'm using a Dragon/6809 based machine and want to add a dedicated PIA?

You've come to the right place! There is a wealth of stuff covering expanding Dragons and adding PIA's, address decoding etc. Goto the Add-ons page and read up on address decoding methods, PIA interfacing and decide how you want to do it.

I'm using a Dragon and want to use the printer port?

Remember, drivers aren't yet available for this option. To make the mod necessary, open up the dragon and locate the printer port. Adajacent to the port is a 74LS244. This needs to be removed (desoldered or chopped out whatever) and wire links soldered in as follows:

    Pin 2..9 to pins 18..11
I intend to use an Intel 8255 PIO card for my PC?

In the UK, a kit is available (which I used) based around this card which plugs into a standard ISA slot from Maplin Electronics. Contact:

     Maplin MPS
     PO Box 777
     Rayleigh
     Essex
     SS6 2BR
     UK

     pt no: LP12N, £27.99 (kit)
            AM11M, £34.99 (assembled)
For international enquiries and orders ring: 44 1702 554000

In the US http://www.boondog.com also supply these type of cards which conceivably could be used. (info courtsey John W. Linville).

I intend to use the LPT port on my PC?

Firstly, it needs to be a dedicated port, so you will need to buy and add one on if you do not have one spare (or add a printer switch box). See the PC-Share V4 Users Manual for information on determining which port to use.

I need to connect up my PC to my remote computer?

Get the PCShare V4 Users manual, this covers the connections for all combinations of port you may wish to use.

I need to test out the link?

Get the PCShare V4 Users manual - this contains QBASIC and Dragon BASIC code examples for driving an 8255 PIO and 6821 PIA. For other chips you will need to understand how to program your IO controller - you'll need to do this anyway to write your driver code.

I'm not using an 8255 PIO and need to write a new PC-Share driver?

Get the PCShare V4 Users manual. This contains full details on how to go about using the development kits shipped with PCShare.

I'm not using 6809/OS9 based machine and need to write driver software for my computer?

To write the basic IO drivers, you need to understand the port you are using - you should have done this when you tested the link out. Get the Data Interface Protocol document to understand the messaging system PC-Share utilises and decide how you are going to implement your software - as part of the operating system or separate utilities. If you understand 6809/OS9 assembler then the source code modules provided with the OS9 drivers should be of some guidance.

I'm using a 6809 based machine but not running OS9

See the previous section, but definately get the OS9 source code.

I'm using OS9 and need to write drivers for a different IO chip/protocol?

Download the OS9 drivers which includes source code for all of the low level drivers and make the necessary changes to the code included with it.

Get a new PC-Share version or keep track of latest development progress?

The main PC-Share page is the starting point, but the latest development progress section is updated fairly regularly. Or drop me an e-mail. Feeback is always appreciated, particularly with suggestions about new features or support for other protocols or interfaces - I am well aware that the 8255 PIO only support has been limiting, hence the up and coming LPT support for example.

Last Updated: 07th Aug 1999