Instruction manual

Introduction

The CPUville Disk and Memory Expansion Board is designed to provide the CPUville Z80 computer

with 64K RAM memory and an IDE disk interface, allowing the computer to run a disk operating

system, such as CP/M

. If CP/M is installed, this gives you access to hundreds of programs in the

public domain that will run on the Z80 computer. You need the CPUville serial interface board in order

to operate the computer with the disk and memory expansion attached.

The disk interface is an IDE interface (also known as parallel ATA, or PATA), that will accommodate

an IDE-compatible drive, including compact flash and SD drives with the appropriate adapter. Only the

lower 8 bits of each disk data word are transmitted to the Z80 system, so drives that operate in 16-bit

mode will have only half the disk space available. This is a trade-off to keep the price of the kit low,

because extra hardware would be needed to capture all 16-bits, and convert it to 8-bits for the Z80 data

bus. However, since the PATA interface has been replaced by the serial ATA (SATA) interface in

commercial computers, IDE drives are now obsolete, and IDE drives with sizes of hundred of

megabytes or even gigabytes are very inexpensive. 8-bit programs are very small, so literally thousands

of Z80 programs would fit into a disk space of 100 megabytes. If you have an IDE drive of a few

hundred megabytes or more, you can run CP/M and store all the 8-bit data you could reasonably want

using the CPUville Z80 computer with the disk and memory expansion.

Testing has shown that not all mechanical IDE drives will work with the current version of the disk and

memory expansion board and ROM program. This instruction manual includes a Table of Tested Disk

Drives on page 80 that shows which drives work and which don't. I am trying to figure out why some

drives don't work. I will update the list of drives as I find out more.

Power for a disk drive that requires only low-current +5V, such as a solid state drive, can be provided

by the logic probe connector on the computer board, or by pin 20 on the IDE connector, as described in

detail in the section “Building the Disk and Memory Expansion Board” below. Power for a drive that

requires +12V, or a drive that draws a lot of current from the +5V supply, will need to be provided by

an appropriate power supply. Usually, a hobbyist will have an old computer system power supply that

can supply both the regulated +5V for the computer, and +12V for the disk drive. These power supplies

can also be obtained cheaply. If two separate power supplies are used, they need to share a common

ground.

When the disk and memory expansion board is attached to the Z80 computer, the memory and

input/output ports on the main computer board need to be disabled by removing jumpers JP1 and JP2.

This is because the disk and memory expansion board provides the computer with a new set of

input/output ports and memory ICs. Of course, if the disk and memory expansion board is removed,

replacing the jumpers restores the ports and memory of the computer board to their original condition.

You do not need to physically remove the ROM or RAM from the computer board when they are

disabled.

The memory expansion provides two memory configurations. Configuration 0 has 2K of ROM from

location 0x0000 to 0x07FF, and 62K of RAM from 0x0800 to 0xFFFF. Configuration 1 is all-RAM,

that is, it has 64K of RAM from location 0x0000 to 0xFFFF. The configurations are selected by

1 CP/M is a registered trademark, currently owned by Lineo, Inc.