Ah the interrupt handling a bunch of unnecessary things... Z80 has IM 2, you set a page-aligned 256 byte buffer, point the I register, enter Interrupt Mode 2,

Ah the interrupt handling a bunch of unnecessary things... Z80 has IM 2, you set a page-aligned 256 byte buffer, point the I register, enter Interrupt Mode 2, then you have your own custom interrupt handler instead of the one provided by the ROM.