The ZIP Parallel Interface
Author Mike Andrew

This document covers the ZIP 100 and 250 Megabyte parallel drives. The protocol and handshakes described might be the same for Clik, Jaz and LS120.

Which drivers?

There are three different modules for zip drives.

• ppa.o Old chip
• imm.o New chip
• zip.o    Combined module for old and new.

There are two different chipsets employed in the IOMEGA.

1. "ppa" (parallel port adaptor) VPA
2. "imm" VPA2

Timing and protocol for each chip is different. Linux uses two separate drivers ppa.o and imm.o respectively, and the Step site provides a third alternative, zip.o  to combine both.

For clarity, this document states 'zip' instead of ppa/imm/zip.o. Where appropriate, the specific module is mentioned.

General Information.

Kernel Module Topology

           The SCSI Interface

Module Overview

        detection

        Protocol Handhsake

Mode Timing Diagrams

    Data Transfer

        ZIP Nibble Mode

        ZIP Byte Mode

        ZIP EPP Mode

    ZIP PPA Connection Timing

    ZIP IMM Connection Timing

    IMM Negotiate and Acknowledge

    ZIP Reset Sequence

ZIP interface Status