Tiny url http://tinyurl.com/jdp3qqr
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The Z88 only uses one half of this dual decode chip. This circuit may be made with
- 3 inverters
- 2 NAND gates
The inverters are slower than the NAND gates, so it was decided to use 5 NAND gates using 3 of the gates as inverters.
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| Part No | Chip | Manufacture | Speed nS | Package | Price | |||
|---|---|---|---|---|---|---|---|---|
| Min | Typ | Max | ||||||
| 1741279 | SN74LVC1G139DCTR | Ti | <2.5 | SM8 | $ 0.69 | |||
| SN74LVC1G139DCUT | Ti / Farnell | <2.5 | VSSOP | £0.404 | ||||
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| Part No | Chip | Manufacture | Speed nS | Package | Price | |||
|---|---|---|---|---|---|---|---|---|
| Min | Typ | Max | ||||||
SN74LVC1G0832 | Ti | <2.5 | SOT-23 (DBV) | $ 0.69 | ||||
| SN74LVC1G139DCUT | Ti / Farnell | <2.5 | VSSOP | £0.404 | ||||
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| Inputs | Outputs | ||
|---|---|---|---|
| B /CE | A A19 | /Y1 /CE1 FLASH | /Y0 /CE0 RAM |
| 0 | 0 | 1 | 0 |
| 0 | 1 | 0 | 1 |
| 1 | X | 1 | 1 |
Circuit Diagram using a single decode chip.
http://tinyurl.com/h9nw253
Updated 3/10/2016
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Building the circuit on a breadboard externally
Components required
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(This picture needs replacing)
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2 MSOP-8 AND 1 VSOP to IC adaptors were obtained in addition to the 5 2-to-4 Line Decoder chips.
This circuit could now be bread-boarded and tested outside the Z88 card case.
The four signal and power lines can be seen connecting the card to the breadboard.
The Games play without crashing.
Circuit Diagram using the Single 3-Input Positive AND-OR Gate and a single decode chip.
To be drawn
Building the circuit on a breadboard externally
Components required
|
|
|
|
2 MSOP-8 AND 1 VSOP to IC adaptors were obtained in addition to the 5 2-to-4 Line Decoder chips.
This circuit could now be bread-boarded and tested outside the Z88 card case.
(This picture needs replacing)
photo needs to be replaced
The four signal and power lines can be seen connecting the card to the breadboard.
(This picture needs replacing)Plan view showing all the connectionsto be replaced.
The Games play without crashing.
Oscilloscope Readings
(This picture needs replacing)
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