Change the V0.8 board to the V0.9 schematic.

A15 issue
---------

The usage of A15 as Chip Select is inverted, the EF9345 needs a 
non-inverted A15, while the EEPROM needs an inverted signal.

- Cut trace between U6-21 and U6-22 (component side)         Vcc
- Cut trace between U6-22 and U4-20 (solder side, below U4)  A15
- Cut trace between U1-6 and U7-26 (solder side, below U1)  ~A15

- Add wire from U1-6 to U4-20  ~A15
- Add wire from U6-22 to U7-26  A15

2022-11-23


EPROM select issue
------------------

The timing of a data read is not regulated with an inverted R/~W, but with ~(R/~W AND E). 
** Speculative: an inverted E might work better if no NAND is available.**

- Cut trace between U6-38 and U1-9 (solder side, below U1)   R/~W

- Add wire from U6-40 to U1-9                                E


Data bus issue
--------------

The data output pins of the EPROM (U4) and VDU (U7) are reversed.

- Cut trace between U6-37 and U4-19 (solder side, below U4)  AD0
- Cut trace between U6-36 and U4-18 (solder side, below U4)  AD1
- Cut trace between U6-35 and U4-17 (solder side, below U4)  AD2
- Cut trace between U6-34 and U4-16 (solder side, below U4)  AD3
- Cut trace between U6-33 and U4-15 (solder side, below U4)  AD4
- Cut trace between U6-32 and U4-13 (solder side, between U4 and U6)  AD5
- Cut trace between U6-31 and U4-12 (solder side, between U4 and U6)  AD6
- Cut trace between U6-30 and U4-11 (solder side, between U4 and U6)  AD7

- Add a wire between U4-11 and U6-37  AD0
- Add a wire between U4-12 and U6-36  AD1
- Add a wire between U4-13 and U6-35  AD2
- Add a wire between U4-15 and U6-34  AD3
- Add a wire between U4-16 and U6-33  AD4
- Add a wire between U4-17 and U6-32  AD5
- Add a wire between U4-18 and U6-31  AD6
- Add a wire between U4-19 and U6-30  AD7


IRQ & NMI issue
---------

The current button is active in the RESET signal, it should be on the IRQ signal.
For the old print, the existing switch is reused, the new board will have space for two switches.
THE NMI and IRQ signal are currently unconnected.

- Cut the trace between SW2 and D1 (component side),
- Cut the trace between SW2 and R12 (solder side),

- Solder an 1 kOhm resistor on the +5V side of R12, (R13)
- Solder the other side of the 1 kOhn resistor to the 'RESET' side of SW2,
- Add a wire between the junction of the new 1 kOhm resistor and SW2 to U6-5 (IRQ),
- Add a wire between U6-4 (NMI) and U6-8 (pullup resistor).