Notes from my Spectrum +3 manual

I've recently been working on a full HTML5 conversion of the Sinclair Spectrum +3 manual with full canvas-drawn screenshots and diagrams for smooth scaling/high res displays as well as some close font matching and layout as well as cross-reference links all over the place. More on that in the future.

What I wanted to show today was the odd commands, pokes and outs that were hastily scribbled down in the back of my manual over the years.

Spectrum +3/+2A specific

  • You know you can type SPECTRUM to go from +3 BASIC to 48K BASIC but, did you know you can get back? RANDOMIZE USR 23354. It leaves CHR$ 163/164 as UDGs.
  • Switch off the +3 drive with POKE 23399,4. In 48K mode, you can use POKE 23611,221 if it somehow stayed on.

128K specific

  • 128K machines are very compatible but the last two user-defined graphics (UDGs) T and U have become the SPECTRUM and PLAY command (for switching to 48K mode and using the AY-3-8912 sound chip). You can, however, switch them back to UDGs using POKE 23611,205.
  • POKE 23611,205; RANDOMIZE USR 4867; alternative way to switch from 128K to 48K.

A couple of VTX-5000 modem specific hacks:

  • OUT 8189,0 to switch the 128K ROM back in.
  • POKE 23611,29 also to switch from 48K to 128K mode.

All machines

  • POKE 23617,n changes the input mode for INPUT prompts. 0=Alpha (C/L), 1=Extended (E), 2=Graphics (G), 4=Keyword (K).
  • POKE 23658,0 turns off CAPS LOCK while POKE 23658,1 turns it on.
  • POKE 23692,255 will suppress the Scroll? prompt 255 times so you can auto-scroll.
  • RANDOMIZE USR 3582 to scroll the screen one line.
  • RANDOMIZE USR 3330 to scroll the entire screen.
  • LET A=32768: POKE 23607,A/256: POKE 23606,A-(PEEK 23607 * 256)

A few pokes to stop people messing with your BASIC programs!

  • POKE 23756,n to change the first line number to n. If you set this to 0 then, it is not editable without reversing the poke! In 128K mode it lists line 0 over and over and can cause the editor to crash while adding new lines!
  • POKE 23613,82 will disable the BREAK key in your BASIC program
  • POKE 23613,0 causes BREAK to crash.
  • POKE 23755,100 causes the program listing to be invisible on BREAK while running (use POKE 23755,0 to get it back)

Header-less tape loading and saving...

LD A,255
JP 1218 ; Save or
JP 1366 ; Load



1 responses

  1. Avatar for jezza

    Hey man! Thank you very much! I have been looking for the BREAK command for years!

    jezza March 19, 2021