* While the syntax of the 8-bit ADD, ADC and SBC instructions all explicitly mention the A register, the SUB instruction does not mention it. On the Zilog eZ80, the SUB instruction explicitly mention the A register.
* IN r,(C) and OUT (C),r instructions syntax is misleading as these instructions actually use the full 16-bit port address contained in BC. On the Zilog eZ80, these instructions are correctly named IN, r,(BC) and OUT (BC),r.
* The Amstrad engineers chose to use the high byte of the address (register B) for chip selection instead of the low byte (register C) in I/O operations. As a result, OTIR / OTDR / INIR / INDR instructions cannot be used on Amstrad CPC for transferring or reading a sequence of values on a port as they these instructions use the B register as a counter.
* INI/IND/INIR/INDR decrease B after storing the byte from the hardware port into memory. And OUTI/OUTD/OTIR/OTDR decrease B before sending the memory byte to the hardware port. [https://www.cpcwiki.eu/forum/programming/z80-documentation-errors/ Source]
* All PUSH and POP instructions utilize a 16-bit operand and the high-order byte is always pushed first and popped last. PUSH HL is PUSH H then L. POP HL is POP L then H.