Rozkaz NONI

Z ZX Spectrum Wiki

This document makes use of an imaginary instruction with the mnemonic NONI (No Operation No Interrupts). Its interpretation is 'perform a no-operation (wait 4 T-states) and do not allow interrupts to occur immediately after this instruction'. The Z80 may actually do more than just a simple NOP, but the effects are irrelevant assuming normal operation of the processor.

http://www.z80.info/decoding.htm