Introduction to Data Communications
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Packet drivers use software interrupts to identify the network cards to the data link layer. Packet drivers are free software drivers that were developed to address the problems of running multiple protocols over one network card. NDIS and ODI are proprietary schemes that have been developed by 3COM/Microsoft and Novell/Apple respectively to address this problem.

The Crynwr Software collection of packet drivers are available throughout the Internet and they are free to use unlike shareware and commercial products.

Advantages:

• Run multiple applications across the same board: TCP/IP, NetBIOS, Netware
• One board fits all, no buying different boards for different applications.
• No more reconfiguring and rebooting to change applications.
• Connect to a Novell File Server (or servers) and still run TCP/IP or PC-NFS or with the Novell systems remaining active and available for file serving and printing.

The Packet Driver acts as a fast smart secretary, bothering clients only when packets arrive specifically for them.

Software Interrupts

Software interrupts are interrupts generated by software unlike hardware interrupts that are physical lines that run to each device. Software interrupts that are available are 0x60 to 0x66. Table xx-1 lists the software interrupts and their assignments.

The packet drivers are assigned software interrupts to the network interface card during the bootup process usually in the autoexec.bat file. For a 3c503 card the autoexec.bat file would have this line:

where:

• 3c509 calls up the packet driver 3c509.com
• 0x60 is the software interrupt assigned to the NIC
• 5 is the hardware interrupt of the NIC
• 0x300 is the I/O address of the NIC

Any network traffic received or transmitted from the NIC would be addressed by the software interrupt 0x60. Complete documentation is available from the Crynwr collection under the files. Important files to read are install.doc and packet.doc.

Software Interrupts Assignments

	60 -- -- reserved for user interrupt

	61 -- -- reserved for user interrupt

	62 -- -- reserved for user interrupt

	63 -- -- reserved for user interrupt

	64 -- -- reserved for user interrupt

	65 -- -- reserved for user interrupt

	66 -- -- reserved for user interrupt

	67 -- -- LIM EMS

	68 01 -- APPC/PC

	69 -- -- unused

	6A -- -- unused

	6B -- -- unused

	6C -- -- DOS 3.2 Realtime Clock update

	6D -- -- VGA - internal

	6E -- -- unused

	6F -- -- Novell NetWare

 	70 -- -- IRQ8 - AT/XT286/PS50+ - REAL-TIME CLOCK

	71 -- -- IRQ9 - AT/XT286/PS50+ - LAN ADAPTER 1

	72 -- -- IRQ10 - AT/XT286/PS50+ - RESERVED

	73 -- -- IRQ11 - AT/XT286/PS50+ - RESERVED

	74 -- -- IRQ12 - PS50+ - MOUSE INTERRUPT

	75 -- -- IRQ13 - AT/XT286/PS50+ - 80287 ERROR

	76 -- -- IRQ14 - AT/XT286/PS50+ - FIXED DISK

	77 -- -- IRQ15 - AT/XT286/PS50+ - RESERVED

	78 -- -- not used

	79 -- -- not used

	7A -- -- Novell NetWare - LOW-LEVEL API

	7A -- -- AutoCAD Device Interface

	7B -- -- not used

	7C -- -- not used

	7D -- -- not used

	7E -- -- not used

	7F -- -- HDILOAD.EXE - 8514/A VIDEO CONTROLLER INTERFACE

	80 -- -- reserved for BASIC

Introduction to Data Communications
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