Jump to: navigation, search

ZX Spectrum +2A/2B, +3/3B

19 bytes removed, 01:10, 10 November 2015
Proper name of Spectrum 128
| colours = 15 (2 per 8×8 cell)
The ZX Spectrum +3 was released on the 16th of May 1987. It is a significant redesign from the original [[ZX Spectrum+ 128K|"Toastrack" 128K128]] and [[ZX Spectrum +2|Grey +2]] models, with additional memory paging capabilities to support [[CP/M]] and additional ROM containing the [[+3DOS]] disc operating system code. The +3 has an integrated 3″ single sided floppy disc drive.
The "Black +2" appeared soon after with an integrated tape drive. Housed in a slightly modified version of the +2 case moulding cast in black plastic instead of grey.
=====Common hardware specifications=====
* Processor: Zilog Z80A microprocessor clocked at 3.5469MHz.
* ROM: 64KB 64kB ROM. 2×32KB 2×32kB EPROM arranged in 4 pages of 16KB16kB.* RAM: 128KB 128kB of Dynamic RAM, arranged in 8 pages of 16KB16kB.* Graphics: 256 × 192 256×192 pixels, 16 colours, attribute based. See [[Spectrum Video Modes]].
* Sound: AY-3-8912 3 channel, 8 octave Programmable Sound Generator and "beeper". Modulated onto video signal.
* Keyboard: 58 plastic keys with metal springs, operating a plastic membrane.
==Timings and Contention==
The contention and ram timings on the +3 and Black +2 differ significantly from earlier models due to the redesigned [[The Amstrad gate array|gate array]]. Timing patterns and memory contention are described in detail in the [[Contended memory#Black Spectrum +2 (2A, +2A/B) 3, +2B, and +33B|contended memory]] article.
The memory space is divided into four 16k 16kB pages and can be used in two ways; "Standard paging mode" and "Special paging mode".
Paging is controlled by performing I/O writes to ports 0x1ffd and 0x7ffd.
====Standard paging mode====
The 64k 64kB of ROM and 128k 128kB of RAM can be paged into the memory space as shown in the diagram below:
<!-- table of memory pages -->

Navigation menu