ZX Spectrum 128

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  • This article is about the "toastrack" 128K model. For other Spectrum models with 128K of RAM see ZX Spectrum 128K models
Infobox: ZX Spectrum 128
Manufacturer Sinclair Research / Investrónica
Mfg. volume
CPU Z80A @ 3.5469MHz
ROM 32kB
RAM 128kB
as pages 8*16kB
Gfx Res 256x192
Gfx Colours 15 (2 per 8x8 cell)


Hardware

  • Processor: Zilog Z80A microprocessor clocked at 3.5469MHz.
  • ROM: 32KB ROM, arranged in 2 pages of 16KB.
  • RAM: 128KB of Dynamic RAM, arranged in 8 pages of 16KB.
  • Graphics: 256 x 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 above a rubber pad and plastic membrane. Optional editor keypad.
  • I/O: Software controlled RS232 serial port. Keypad Port. Tape In (ear) and Tape Out (mic).

Timings

Paging

The memory space of the Spectrum+ 128K is divided into four 16k pages. The 32k of ROM and 128k of RAM can be paged into the memory space as shown in the diagram below:

0xFFFF
-
0xC000
Bank 0 Bank 1 Bank 2 Bank 3 Bank 4 Bank 5
(screen 0)
Bank 6 Bank 7
(screen 1)
0xBFFF
-
0x8000
Bank 2
0x7FFF
-
0x4000
Bank 5
0x3FFF
-
0x0000
ROM 0 ROM 1

Paging is controlled by performing I/O writes to ports 0x7ffd.

The bits are described in the table below:

Port Bit
7 6 5 4 3 2 1 0
0x7ffd Disable Paging ROM low Active Screen RAM Bank

Keypad