that ROM-based service routines are present at fixed addresses in ROM. Additionally, if the default interrupt mode (IM1) is set, the CPU will JP to 0038h every frame trying to find an interrupt handler routine. If it does not, (which it won't unless you write your own), the system will crash.
ZX Spectrum Next User Manual, 3rd Edition (ISBN 978-1-5272-5496-1), written and illustrated by Phoebus R. Dokos. Copyright © 2020-2024 Phoebus Dokos / SpecNext Ltd. Licensed under CC BY-NC-SA 4.0. This is a transcription and can contain errors; check any doubt against the printed page.