Spectrum 48

From Grahams Wiki

The spectrum 48 was the first attempt at a speccy. There were a total of 6 versions. I posess a version 2, a number of V3's and a V4 (Although the V4 is a Speccy 48+)

Contents 1 Specification 2 Chip list 3 Add ons 4 My mods 5 IO Ports 5.1 General machine control port 6 Ports 7 My speccy

[edit] Specification

• Z80 running at approx 3.5Mhz
• 48kb of ram
• 16kb of rom
• A beeper

[edit] Chip list

• 3.5Mhz Z80
• 23128
• Astec UM1233 Video modulator
• 6C001E-6 ULA
• 4116 RAM x8
• TMS4532 RAM x8 (Sometimes uses OKI M3732H
• LM1889 Colour chip
• 74157 x4 (Multiplexer)
• 7400 (Quad 2 input NAND)
• 7432 (Quad 2 input OR)
• 7805 Voltage regulator

[edit] Add ons

I have a variety of add ons for this computer:

• RAM TURBO interface (SInclair I/F 2)
• Uncased ZX Inteface 1
• Datel Kempston Joystick interface clone

[edit] My mods

[edit] IO Ports

[edit] General machine control port

This port was the only one used on the unexpanded 48K, and it is used for both keyboard, border and Tape IO.

Write:

• 0 \
• 1 | Border colour (0-7)
• 2 /
• 3 Mic output bit

Read:

This is complex, the LSB of the port outputted is $FE. and the MSB is a strobe for they keyboard line. Each bit returned is one key. so:

• FEFE Shift->V
• FDFD A->G
• FBFE Q->T
• F7FE 1->5
• EFFE 0->6
• DFFE P->Y
• BFFE Enter->H
• 7FFE Space->B

Keys are active low.

[edit] Ports

The computer has the following ports:

• UHF out
• Ear
• Mic
• Sinclair expansion port
• 9v power in

[edit] My speccy

File:Spectrum48.jpg