[img] Sinclair ZX Spectrum Circuit Diagrams
MDFS::Info.Comp.Spectrum.Circuits Search

I am gradually scanning and cleaning up the piles of circuits diagrams I have. These are various bits of Spectrum hardware that I have built and used, and other hardware that I have examined and worked out the circuit diagrams from.
Title   Paper Size Description
Backplane
Ctrl2.gif

diagram
 
654x973 A4P
 
21K
Backplane system for the Spectrum. I prototyped a lot of my hardware with this.
Key+Joy.gif
SpecKbd.jpg
diagram
picture
916x1000 A5P
34K
52K
ASCII keyboard on port &FD/&F9 and Kempston joystick on port &1F.
ExtKbd.gif diagram 2048x2452 A4L 104K Experimental external keyboard interface.
IF1.gif
IF1sm.gif
IF1th.gif
IF1.jpg
diagram
diagram
diagram
picture
4096x2896 A4L
2048x1448 A5L
720x509 A5L
176K
68K
13K
7K
Sinclair Interface 1. Initially drawn by hand in 1987, being redrafted.
1-chip Joystick diagram 50K 2912x2056 A5L 1-chip Kempston joystick interface. Uses just a single 74LS365 hex buffer, a Spectrum edge connector and a 9D plug. This is the type of joystick interface that causes interupt problems in IM2 as it only decodes ~IORQ and A5, so any I/O access with A5=0 reads the joystick. So, an interupt acknowledge with ~IORQ=0, but ~RD=1 and ~WR=1 accesses the joystick.
2-chip Joystick diagram 50K 2912x2064 A5L 2-chip Kempston joystick interface. Uses just a single 74LS365 hex buffer, a single 74LS32 quad-OR, a Spectrum edge connector and a 9D plug. This is the type of joystick interface fully decodes IN 31, so does not interfere with interupts in IM2. The addition of a 35p multiple OR gate decodes ~IORQ, ~RD, A7, A6 and A5 to correctly respond to IN 31.
ROM1.gif
ROM1t.gif ROMBox.jpg
ROMBox2.jpg
diagram
diagram
picture
picture
127K
28K
79K
54K
2912x4096 A4P
264x512 A5P
Single socket external ROM box. Can plug in an 16K or 32K ROM. ROMs selected with OUT &FD,&nn.
b4=0 - external ROM, b4=1 - internal ROM.
b6=0 - lower 16K, b6=1 - upper 16K.
Gives:
  • &00 - external ROM lower 16K
  • &10 - internal ROM
  • &40 - external ROM upper 16K
ROM4.gif diagram 185K 2912x4096 A5P Four-socket external ROM box. Can plug in a combination of 16K and 32K ROMs. ROMs selected with OUT &FD,&nn.
b4=0 - external ROM, b4=1 - internal ROM.
b6-b7=external ROM number
Gives:
  • &00 - 16K ROM 0 or lower 16K of 32K ROM 0
  • &10 - internal ROM
  • &40 - 16K ROM 1 or upper 16K of 32K ROM 0
  • &50 - internal ROM
  • &80 - 16K ROM 2 or lower 16K of 32K ROM 2
  • &90 - internal ROM
  • &C0 - 16K ROM 3 or upper 16K of 32K ROM 2
  • &D0 - internal ROM

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