============================================= Amiga Parallel Port ZIP Drive Adaptor ============================================= v0.0 By Bruce Abbott (bhabbott@inhb.co.nz) Introduction ------------ The Iomega ZIP 100 drive is available with a choice of either a SCSI or a parallel port interface. Unfortunately the parallel version could not be used on an Amiga - until now! This project consists of both hardware and software - a small interface that connects to the Amiga's parallel and joystick ports, and a driver file which causes the ZIP drive to operate like a standard SCSI device. Background ---------- ZIP drives were originally designed to operate via SCSI. Iomega realised that most peecee owners don't have a SCSI interface, so they developed the 'ppa3' chip to interface peecee printer ports to their drive. While this is OK for peecee owners, the Amiga's parallel port is not compatible with this solution. In particular, most of the required control lines are either missing, lacking in functionality, or not strong enough. To make the situation even more hopeless, Iomega did not release any specs for their interface chip. Recently I noticed that a Linux parallel port ZIP driver has appeared, thus solving the software specification problem. By examining this I was able to determine how to send commands to the ppa3 chip and what responses to expect. I then grafted this code onto a PD SCSI driver (Spartan 34.4). As the Amiga parallel port does not have enough I/O lines, I used the joystick port for one output and four inputs. I also added a TTL buffer chip (with Open Collector outputs) to increase output current capacity on the control lines. Building the Interface ---------------------- You need:- 1 D25 plug 1 D25 socket 1 D9 plug 1 7407 TTL buffer chip or equivalent (with o/c outputs) 1 capacitor (about 1uF) some wire to connect the bits together A neat job can be done by starting with an RS232 jumper box, and a cable robbed off an old joystick. Wire the circuit according to the included diagram. Please check your connections carefully, as incorrect wiring could fry your Amiga's CIA chips! Installation ------------ Plug the hardware interface into your Amiga's parallel port and joystick (Game2) port, and attach your ZIP drive to its output. Copy the driver 'ppazip.device' to your DEVS: drawer. Also, copy the mountlist 'ZIP0' to anywhere you want (eg. Storage/DOSdrivers). If you have a Modem plugged in at the same time, make sure that its Ring Indicator line (pin 22) is disconnected. Otherwise an incoming call might interfere with the ZIP drive (this can also cause trouble with printers, and is due to RI being connected to SEL in the Amiga). Performance ----------- It's not fast. However, the results are quite good for a parallel port interface - much faster than Parnet for example. Whilst the driver is necessarily CPU intensive, it does not disable multitasking or block interrupts. No errors occured when downloading files using ZModem protocol at 28,800baud, directly to the ZIP drive. Here's a DiskSpeed 3.1 report, from my A1200 with 68030/40MHz. Device: ZIP0: Test Intensity: Low Performance Stress: None 13 Files/s Create 19 Files/s Open/Close 48 Files/s Scan 51 Files/s Delete 925 Seek/Read Buffer Size 512 4096 32768 262144 ----------- --------- --------- --------- --------- Bytes/s Create 23831 89478 100312 108590 Bytes/s Write 24559 93433 105475 113599 Bytes/s Read 24646 93426 105323 113615 Limitations ----------- Currently the device does not check for disk changes. You must run 'diskchange' to log on a new disk. (I don't yet know how to do SCSI media change detection!). SCSI Direct commands are not supported, which may prevent programs such as 'ZIPTools' from functioning. Therefore you probably won't be able to remove write-protect passwords etc. The ZIP's printer passthrough doesn't work. This is due to the control lines being routed to different pins by the adapter. Of course you can't print while the driver is active anyway (since it needs exclusive use of the parallel port). Because the interface uses your joystick port, some games may be unplayable. Bugs ---- Due to the lack of diskchange detection, if you remove the disk and then try to access it a read error will probably occur. Just put the disk back in and hit 'retry' a few times :-) If the drive goes to sleep (due to no access for a long time) errors may occur on subsequent accesses. To avoid this, eject the disk and re-insert it _before_ accessing the disk. Legal ----- This project is Public Domain. Do with it as you wish, but don't blame me if you damage your Amiga, ZIP drive or anything else! It might trash files on your ZIP disks, so don't use it for anything important unless you make backups first. Bruce Abbott (bhabbott@inhb.co.nz)