A little card to use two card (Sound or IO card) using the both IN or OUT address.
This release only work with one IORQ address, but it can be use to filter a specific address.
SW2 is use to set a high bit in the address=1.
SW1 is use to set a Low bit in the address=0.
In IRQ = $1F = %00011111
SW1= %11100000
SW2= %00011111
(SW1 Will be the SW2 Xor $FF value.)
SW3 Will be the IORQ sent to the slave card.
Kicad Project:
http://zx81.ordi5.free.fr/brico/ZX81_IORQ_Converter