

EtherLan Drivers:
Virtual Ethernet Interface (EtherH v.4.15 or later)
Release Note


EtherLan is a trademark of  i3 Ltd.
ACORN, ARCHIMEDES and ECONET are trademarks of Acorn Computers Ltd.
Ethernet is a registered trademark of Xerox Corporation.

Copyright  1996,  i3 Ltd.
Document no. Virt:110, Issue 1.1, 8th July 1996


Overview
========
Ethernet supports a number of different network protocols, all of which are 
accepted by the i3 Ethernet cards. However, in some situations a single computer 
may appear on a network as two different network clients. The situation where 
this is likely to occur is when the computer is fitted with a PC Card (podule 
card or PC second processor card). Two complete processing environments are 
operating side-by-side, under the PC and the RISC OS operating systems 
respectively. You have two computers operating in a single case, connecting to the 
Ethernet network through a single interface card. When one or other of these 
environments is initialised it looks for support for the the network protocols it 
requires, claiming them from the interface card. Thus the two processors can 
co-exist side by side provided there is no overlap between the network protocols 
they wish to use. 

For those computers which can support a second processor (A5000, Risc PC and A7000)
the versions of EtherH, the i3 Ethernet driver, from 4.15 onwards, offer the 
additional feature of Virtual Ethernet Interfaces. This means that the single 
hardware Ethernet interface card can appear to the network as two distinct 
connections, and can offer the PC processor and the RISC OS environment independent 
connections to the network. This means there is no restriction on the networking 
protocols available to each processor - each of them can use all the protocols. 
Because virtual interfaces present a small processing overhead (especially on a 
busy network), and are not needed in all circumstances, the user may configure the 
feature on or off.

This Application Note describes the changes in the Ethernet driver; it updates 
information provided in the EtherLan User Guide (Issue 2.0: 10 Jan 1996) and in 
the Application Note: 
    Using a PC card with your i3 Ethernet card (Issue 1.0: 21 Feb 1996).

Applicability
=============
The information given in this release note only relates to the Ethernet driver 
supplied for use with the E500 series and E600 series EtherLan interface cards; 
drivers for the E100 and E200 series cards remain as described in the EtherLan 
User Guide. The new driver - EtherH version 4.15 or later - may be provided as part 
of a Flash ROM upgrade, or may be provided separately for "soft-loading" during a 
computer's boot sequence. In this second case it will be supplied as a file called 
EtherH16.

Commands
========
The new driver release introduces a single new configuration command, 
Configure EHVirtual. In addition, when EHVirtual is configured ON the output from 
the EHTest and EHInfo commands is changed. In all other respects the commands 
remain as described in the EtherLan User Guide.

*Configure EHVirtual
Determines whether or not the virtual Ethernet interface feature is activated.
Syntax
	*configure EHVirtual On|Off
Use
EHVirtual is configured On to activate the virtual Ethernet interfaces. 
Thereafter the interface card will present two Ethernet interfaces (eh0 and eh1) 
to the computer. The default configuration state is Off, and EHVirtual should 
only be configured On if there is a PC card (podule card or second processor card) 
installed in the computer and both that card and the RISC OS environment wish to 
use the network.

Example
	*configure EHVirtual On
Related Commands
	None
Notes
	As with any configuration command the current EHVirtual configuration 
        can be found by entering:
	   *Status EHVirtual
	from the command line * prompt.

*EhInfo/*EHTest
The syntax and use of these commands remains as described in the EtherLan User 
Guide; please refer to that Guide for explanation of these commands. However, 
with EHVirtual configured On the information returned by the commands will be 
considerably extended:

Example
*ehinfo
DCI version	4
Card Info:-	i-cubed ltd, EtherLan 600 Ethernet interface
                  	Unit 0, slot 8, 16-bit driver.
                 	Ethernet address=00:c0:32:00:16:30
                  	10Base2 (coax) interface in use.
I/O stats:- 	Rxframes=2319, Rxerrs=4, Txframes=55, Txerrs=0, DMAframes=0
                  	Collisions=4, Rejects=36183
Interface:- 	Twisted pair interface:- link is good, polarity is correct
Rx errors         	fae=1, crc=4, frl=0, ovrn=0
Frame Info:-      	Type=IEEE FrmLvl=4 AddrLvl=2 ErrLvl=0 Handler=224fb08
                 	Type=8035 FrmLvl=1 AddrLvl=1 ErrLvl=0 Handler=218af0c
                  	Type= 806 FrmLvl=1 AddrLvl=1 ErrLvl=0 Handler=218af0c
                  	Type= 800 FrmLvl=1 AddrLvl=1 ErrLvl=0 Handler=218af0c        
Controller Mode:- Promiscuous, reject frames with errors
Card Info:-      	i-cubed ltd, EtherLan 600 Ethernet Virtual interface
                  	Unit 1, slot 8, 16-bit driver.
                  	Ethernet address=00:c0:32:80:16:30
                  	10Base2 (coax) interface in use.
I/O Stats:-       	Rxframes=954, Txframes=560

Frame Info:-      	Type=IEEE FrmLvl=4 AddrLvl=2 ErrLvl=0 Handler=2273598
              	Type=8035 FrmLvl=1 AddrLvl=2 ErrLvl=0 Handler=2273598
                  	Type= 806 FrmLvl=1 AddrLvl=2 ErrLvl=0 Handler=2273598
                  	Type= 800 FrmLvl=1 AddrLvl=2 ErrLvl=0 Handler=2273598        
Controller Mode:- Promiscuous, reject frames with errors

Additional Notes
1. The first section of the output, down to and including the Rx errors line, relates 
   to the first virtual interface (Unit 0, or eh0) and to the physical hardware; any 
   Transmit/Receive errors will be reported in this section of the output. 
2. The Rx errors line will be absent if there have been no receive errors.
3. There will be an additional line, TxErrors, in the first section of the output, if 
   there have been any transmit errors.
4. The second section of output, starting from the second set of Card Info, relates to 
   the second virtual interface (Unit 1, or eh1). This will only show the number of 
   Ethernet frames sent to/from this virtual interface; it cannot have any 
   error/collision/reject information.
5. If no second task has been initialised (e.g. the PC card software has not been 
   started up) then the second section of output will show, after its Card Info:
I/O Stats:-       	Rxframes=0, Txframes=0
Frame Info:-      	No frame filters setup
Controller Mode:- 	Normal, reject frames with errors

6. Frame Type = IEEE was presented as Type = 0 in previous software releases.

Use of the EHVirtual Feature
============================
Setting Up PC Card/Processor Software
-------------------------------------
This remains exactly as described in the Application Note: 
    Using a PC card with your i3 Ethernet card 
except:
* The Ethernet driver must be identified as eh1 (rather than eh0).
* There are no possible conflicts in deciding which protocols to claim when RMEnsuring 
  the PCNE2 module.

Note that it remains possible to use the PC Card/Processor with EHVirtual configured 
Off, in which case the Application note applies "as is", with the driver still being 
identified as eh0.

Virtual Ethernet Interfaces
---------------------------
With EHVirtual configured On the EtherLan interface card effectively presents two 
Ethernet connections to the network. Internally, these are identified as eh0 and eh1, 
with eh0 being claimed by the RISC OS operating system and eh1 being available for a 
network connection from a PC card. 

It may be necessary to configure other software to recognise the two virtual interfaces 
in the computer. In particular, if both RISC OS and the second process are using TCP/IP 
then each virtual interface will need to be given its own unique IP address, and both 
of these addresses should be included in all Host files on the network.



i3 Ltd, Rustat House, 62 Clifton Road, Cambridge, United Kingdom, CB1 4GY
Facsimile: 01223 566313     e-mail: support@i-cubed.co.uk

Release Note: Virtual Ethernet Drivers
Virt:110, Issue 1.1





