PI Packet Driver Notes (January 1992)
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See the file copying.doc for important information regarding this software.

Many of you have asked for a packet driver for the Ottawa PI card which
is compliant with the specification from FTP Software, Inc. The second
release is now available. It has been tested with several NOS variants
and found to be functional. Not all the features of the compiled-in
driver are implemented though, so don't throw out your existing NOS
with PI card support!

It should be noted that any application used with this driver must be
able to understand AX.25 formatted packets. In other words, the only
practical use for it right now is to enable you to use variants of NOS
which do not have PI card support compiled-in.

There is an exception to this rule. The driver may be re-assembled to provide
"simulated ethernet" support, ie, the card can be made to look like
an ethernet card to application software. See the comments in pi.asm for
details.

Limitations of this release:

1. Only the A port (high speed port) works.
2. Unlike the built-in driver, parameters must be specified on the command
line at the time the driver tsr is installed. They can't be changed
while NOS is running.
3. There is no status command.

Install the driver (pi.com) with the command:

pi [hw_int] [io_addr] [dma] [baud] [TXD] [P] [slot] [tail]
[clocking mode] [Buffer size] [Number of buffers]

The parameters are as follows:

packet_int: Software interrupt number the driver uses to communicate
with the application.

hw_int: The hardware interrupt in use. (set by a jumper on the card).
The interrupt least likely to conflict with other hardware
is IRQ 7.

io_addr: The address of the PI card IO registers (jumper).

dma: The DMA channel in use (jumper). Usually channel 1.

baud: The desired baud rate when internal clocking is used.
Set to zero if external clocking is desired (as when using
the WA4DSY modem).

TXD: The transmit delay time in milliseconds. This is the time
which flags are sent before the actual data is transmitted.

P: Probability factor for the P-persistance algorithm (0..255).

slot: Slot time in milliseconds for the P-persistance algorithm.

tail: Delay time to allow the CRC and closing flag to be transmitted
before the transmitter is turned off. This value is calculated
by the driver if internal clocking is used, but may be over-
ridden from the command line if desired (value in msec.).

clocking mode: (new in version 2) If internal clocking is used (the baud
parm is not 0), this parameter gives further control over the
clocking. If it is 0 (default), the receive clock is recovered
from the received data, and NRZI coding is used. This mode is
suitable for driving a modem which does not provide external
clocking signals. The maximum baud rate in this mode is
28,800 bits/sec.

If clocking mode is set to 1, a clock signal is output on
A-TXC, while receive clocking is derived from A_RXC. NRZ
coding is used. This mode is useful for connecting PI cards
back-to-back for example, because higher baud rates can be
obtained. I have obtained 460,800 bits/sec using this mode
(your milage may vary).

A secondary effect of choosing mode 1 is that the baud
rate is 32 times that specified by the baud parameter.

buffer size: This parameter allows you to specify the amount of memory
to reserve for DMA buffers. The default size is 2048.

number of buffers: The number of DMA buffers allocated to the driver. The
default is 5, and the minimum is 3.

For example:
pi 0x7e 7 0x380 1 0 15 128 10 1 0 2048 5

If any parameters after the first one are left off, defaults as shown in the
above example will be used. These are typical parameters for use with the
WA4DSY modem. If the first one is left off, the driver will complain.

If you are using NOS, the attach command in autoexec.net should
look like this:

attach packet

For example:
attach packet 0x7e pi0a 1 2000 your_IP_address

Make sure that you use a TCP MSS which is at least 40 bytes less than the
MTU. Also, best results will usually be obtained with TCP WINDOW = TCP MSS.

Please report your experiences with the driver to me, good or bad.

Dave Perry
VE3IFB
[email protected]
ve3ifb@ve3jf.#eon.on.can