Zde je odkaz na originální stránky pana Granta o ZX80/81
Překlad mám pouze této části:-----------------------------------------------------------------
CONNECTIONSPlease refer to the existing ZX80 circuit when following these instructions.
Below are the connections required to add the prototype NMI circuit to the ZX80 board described on my other page.
This circuit is incorporated into the existing ZX80 circuit as follows:
/WAIT, /HALT, /NMI, A0, A1, /M1, /IORQ
These signals are taken from the Z80 CPU.
/PHI
Taken from IC18 pin 8.
/IORQ + /WR
Connected to IC17 pin 6.
NMI GEN ENABLE
This can either be connected to a SPDT switch, to allow it to be connected to either Vcc or Ground (must always be connected to Gnd when running the ZX80 ROM) or, if you have used a 16K EPROM on the ZX80 containing both images on there (ZX80 image in 0-4K, ZX81 image in 8-16K), then this can connect to the ZX80/ZX81 ROM selection address (A13) on the EPROM for automatic enabling for ZX81 and disabling for ZX80 running.
IC11 PIN 10, IC11 PIN 11 (The Sync logic disable)
The connection between IC11 Pin 10 and IC 11 Pin 11 is broken. This can be achieved by bending out pin 11 on IC11 and soldering the appropriate connection to the bent-out pin. The other connection can be attached directly to the underside of the ZX80 PCB.
IC5 PIN 9, IC16 PIN 10 (The video logic disable)
The connection between IC13 Pin 10 and IC 16 Pin 10 is broken. This can be achieved by bending out pin 10 on IC13. The connections can be attached directly to the underside of the ZX80 PCB.
VIDEO IN
Connected to IC20 Pin 6.
VIDEO OUT
Lift the right-hand side of R30 from the ZX80 board and connect this line to the lifted leg of this resistor.
OLD /SYNC IN * (shown on "optional" circuit)
Connect to IC19 Pin 5 on the ZX80 board. Unlikely to be needed, though, and can be omitted.
/SYNC OUT *
Lift the right-hand side of R32 from the ZX80 board. Bend out Pin 1 of IC21.
Connect the lifted leg of the resistor to the bent out pin on IC21 with a short length of wire. Then, connect this to the /SYNC OUT on the NMI board.
* - Alternative SYNC OUT (more "faithful" to the original ZX81 - HSYNC glitches present on "Save" Mic signal)
Instead of the above OLD /SYNC IN and SYNC OUT modifications shown above, do the following...
Bend out IC19, Pin 5. (Alternatively, remove IC19, as it is no longer needed).
Connect /SYNC OUT to the track connecting IC21 Pin 1, R32 and R35.
If OLD /SYNC IN is also needed, also bend out IC18 Pin 1, connect with a short wire to the bent-out pin 5 on IC19, then connect to the OLD /SYNC IN.
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Ještě poznámka:
Nemám originální ROM. Jirka (NOSTALCOMP) mi nahrál do EPROM 8kB ZX81 + další 3 banky s ZX80. Ale já mám tuto EPROMku pevně nastavenou A13 - z desky ZX, A14 - log. 0, A15 - log. 0.