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README.ppa (c) 1996   Grant R. Guenther,  grant@torque.net

README.ppa (c) 1998   David J. Campbell,  campbell@torque.net

         The IOMEGA PPA3 parallel port SCSI Host Bus Adapter

                     as embedded in the ZIP drive

This README documents the Linux support for the parallel port version of

IOMEGA's ZIP100.  The ZIP100 is an inexpensive and popular, but relatively

low performance, removable medium disk device.  The drive is also available

as a regular SCSI device, but the driver documented here is for the

parallel port version.  IOMEGA implemented the parallel port version by

integrating (or emulating ?) their PPA3 parallel to SCSI converter into

the ZIP drive.

I have implemented a low-level driver, ppa.c,  for this parallel port

host bus adapter, thereby supporting the parallel port ZIP drive as a

regular SCSI device under Linux.

It is possible that this driver will also work with the original PPA3

device (to access a CDrom, for instance). But, the PPA3 is hard to find

and costs as much as the ZIP drive itself, so no-one has actually tried

this, to the best of my knowledge.

The driver was developed without the benefit of any technical specifications

for the interface.  Instead, a modified version of DOSemu was used to

monitor the protocol used by the DOS driver, 'guest.exe', for this adapter.

I have no idea how my programming model relates to IOMEGA's design.

(One technical consequence of this method:  I have never observed a

SCSI message byte in the protocol transactions between guest.exe and

the ZIP drive, so I do not know how they are delivered.  My working

hypothesis is that we don't have to worry about them if we don't

send linked commands to the drive.)

I'd like to thank Byron Jeff (byron@cc.gatech.edu) for publishing his

observation that the 'guest' driver loads under DOSemu.  His remark was

the stimulus that began this project.

For information about using the ZIP drive, please read the generic

instructions in the SCSI-HOWTO and the man pages for the normal disk

management tools,  fdisk, mkfs, mount, umount, etc.  There is a mini-HOWTO

circulating concerning the use of the normal SCSI version of the ZIP

drive, most of its comments will apply to disks connected through the

ppa driver as well.

>------------------------------------------------------------------------<

David Campbell writes:

Since the original was released by Grant several people have made many minor

modifications:

        a) Support for EPP

        b) Autoprobing known parallel ports

        c) Parallel port sharing with other devices (see notes)

It has been found that the JAZ Traveller also uses the VPI0 interface chipset

(a reworked ppa3). This driver will also support this device without

modifications.

Please note that the ZIP Plus drive uses a VPI2 interface chipset (VPI1 never

made it out of the Iomega development lab). A driver for this device exists,

check my web page at http://www.torque.net/~campbell for further details.

                                 -<-->-

Built-in drivers accept parameters using this LILO/LOADLIN command line

syntax (omitted parameters retain their default values):

        ppa=base,mode[,sg_buffer_size]

For example:    ppa=0x378,1

The modes are as follows:

        1       work in standard 4 bit mode

        2       PS/2 byte mode

        3       EPP mode, 8 bit

        4       EPP mode, 16 bit

        5       EPP mode, 32 bit

If ppa is built as a module there is currently no method of changing the

operation of the driver. Basically there is no need (unless you have a very

strange parallel port address).

                                 -<-->-

Using the ZIP drive and a printer either requires two parallel ports (one

for each device) or use of the parport driver (which can be found in the

2.1.x kernels).

In the first case compile the lp driver as a module and load it after ppa.

Alternatively specify which ports the lp driver should use by the LILO/LOADLIN

options:

        lp=base0[,irq0[,base1[,irq1[,base2[,irq2]]]]]

                                 -<-->-

Mainboard buggy chipset hall of shame: [information courtesy of Iomega]

        National Semiconductor PC87306 rev ID 0x70, 0x71

        Winbond xx837

The above chipsets are known to have problems using EPP. Note that the

National Semicondutor problems only affect early batches of PC87306 which

should really never made it to market (a run for mainboard developers).

>------------------------------------------------------------------------<