ZX Spectrum +3 code that reboots BASIC to start loader screen

reboot_tap.asm

    .org	$5CD2			; // fixed origin for https://clrhome.org/asm/ TAP generator	
    di
    xor a
    ld bc, $7ffd
    out (c), a
    ld b, $1f
    out (c), a
    rst $0 ; trick doesn't work when started from ZX Spectrum +3 boot menu right to BASIC48, cause bank switching is blocked forever

test_ram_rom.asm

  ld hl, 0
  ld b, (hl) ; store byte of address 0
  ld (hl), 1 ; write 1 to address 0
  ld a, (hl) ; read byte of address 0
  dec a
  or a
  jr nz, ROM
  ld (hl), a ; write 0 to address 0
  ld a, (hl) ; read byte of address 0
  or a
  jr nz, ROM
  ld (hl), b ; restore byte of address 0
RAM:
...
ROM:
...