ROM Module for RC2014 homebrew computer that supports various page sizes and can be paged out for RAM

What is RC2014?

RC2014 is a simple 8 bit Z80 based modular computer. It is inspired by the home built computers of the late 70s and computer revolution of the early 80s. It is not a clone of anything specific, but there are suggestions of the ZX81, UK101, S100, Superboard II and Apple I in here. It nominally has 8K ROM, 32K RAM, runs at 7.3728MHz and communicates over serial at 115,200 baud.

As a bare minimum, you will need a CPU, ROM, RAM, Clock and Input/Output module. The RC2014 is designed in such a way that you can build your own modules to expand it. As such, if you have access to similar components, or have specific needs, you might not need all the items I have on offer.

What is this module?

This is a Pageable ROM Module that is designed to replace the standard ROM Module on the RC2014. This module offers more features including the option of paging itself out and paging the lower half of the 64K RAM Module in for a full 64k RAM

• Support for 2716, 2732, 2764, 27128, 27256, 27512 (2K, 4K, 8K, 16K, 32K, 64K) EPROM
• Support for 28C series EPROM too. Probably. As yet this is untested though.
• ROM pages of 1k, 2k, 4k, 8k, 16k or 32k on logical boundaries can be addressed through jumpers
• When used with 64K RAM Module, paging out the ROM will enable the lower 32k of RAM
• ZIF Socket Support (See note below)

What do I get?

• Standard Kit This includes all the components to build the Pageable ROM Module including header pins, chips sockets, chips (excluding ROM), jumpers and standard 28 pin socket

• ZIF Socket Kit As above, except a ZIF socket is supplied in place of the standard 28 pin socket (see note below regarding fitting)

• PCB Only Yup, you're right. Only the PCB is supplied with this option

PROM Option

I recommend the use of a 27C512 PROM with this module. This is a non-erasable EPROM and the same type as supplied with the standard RC2014 ROM kit. The one supplied with the standard kit has Microsoft BASIC for a 32k RC2014 supplied in the first 8k, leaving 56k spare for you to use.

If you wish to purchase one with this kit you have 4 options;

• Blank (64k available for your use)
• 32k MS BASIC installed at 0x0000 (56k available for your use) R0000000
• 56k MS BASIC installed at 0x0000 (56k available for your use) k0000000
• CP/M Console installed at 0x8000 and 32k MS BASIC at 0x000. To be used with Compact Flash Module (60k available for your use) R0001000

For ROM label designations, see http://rc2014.co.uk/1515/decoding-rom-labels/

Note - ZIF socket can be used with this module - however, the release bar is fouled by the 74LS32 chips when in the locked position. You can get around this by soldering the 74LS32 direct to the PCB to lower the height, or fit the ZIF socket backwards so the release bar extends on the opposite side, or cut the bar down