ZX81 Homebrew DIY builders Club

General "chat", not necessarily MTX related
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lezanderson
Posts: 175
Joined: 14 Aug 2012 15:31

ZX81 Homebrew DIY builders Club

Post by lezanderson » 14 Jan 2017 14:04

Hi.

Is anyone interested in ZX81 Hardware building/designing and generally messing around ?? Then I'm trying to get interest in a ZX81 Homebrew DIY Microcomputer Club.. all about building designing , modifying etc the ZX81 !!

See:

Sinclair ZX world

http://www.sinclairzxworld.com/viewforum.php?f=7

lezanderson
Posts: 175
Joined: 14 Aug 2012 15:31

Re: ZX81 Homebrew DIY builders Club

Post by lezanderson » 21 Jan 2017 12:37

Mini ZX81 Homebrew Project

Here's an idea for a small and compact ZX81 Design....obvioulsy you'll need to put the ZX81 ULA logic onto the CPLD !!


Specification & Design
Minimum Z80 A CPU 4MJz, 64K SRAM (to run option of CP/M), EEPROM/EPROM, CPLD for all Glue logic, keyboard, memory & I/O decoding etc. Intel 8255 PIO for PATA interface for CF Card or Parallel hard-drive, Real Time Clock RTC to tell time, Date etc & Sound Chips.

Z80 CPU DIP40
64K SRAM (UM71512-15) DIP32
64K EEPROM (W27C512-45) DIP28
CPLD (EPM7128SLC84-15) PLCC84
82C55 PIO for CF Card DIP40
DS12C887 RTC DIP
SN76489 PSG Sound Chip
AY-3-8910 PSG Sound Chip
7805 Regulator

Optional

Maths Co-Processor AM9511
Z80 (84C90xxVEC) KIO giving CTC,SIO,PIO
MAX232 RS232 Driver
MCU micro-conrtroller for PS/2 or USB keyboard
MAX705 IC supervisor (Reset Control)
Floppy Disc Controllers:
MB8877+WD9216
uPD765+SED9240 (as used in ZX Spectrum+3 & Amstrad CPC6128)


Costing (based on ebay.com prices with free international shipping)

Z80 CPU DIP40 ………………………………….…...$1.19
64K SRAM (UM71512-15) DIP32……………….…..$2.16
64K EEPROM (W27C512-45) DIP28………………...$1.0
CPLD (EPM7128SLC84-15) PLCC84………………..$1.96
82C55 PIO for CF Card DIP40……………………….$1.15
DS12C887 RTC DIP ………………………………….$1.20
SN76489 PSG Sound Chip…………………………....$0.99 (2pcs)
AY-3-8910 PSG Sound Chip………………………….$0.99
7805 Regulator………………………………………..$0.50

Total : just over $11.0 (£9.20) for ICs + £2.30 for IC sockets = £11.50

** CPLD is Blank and will need programming using a USB Blaster cable ($3.0 on ebay.com). Altera MAXII software is free on Altera’s Website


Other CPLDs are EPM7160SLC (>$10.0) or EPM9320SLC84 ($20.0 direct Wholesale)
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