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This was thought to be due to an intermittent timing error from the decode chip CD74HCT139 which switches between the RAM and Flash chip but after the Z88 Hardware Investigation, it has been discovered to be a misunderstanding by both the hardware and software engineers on how to write faultlessly to the flash chip. This has only affected a few users, i.e. those who play games in RAM or who do repetitive writing to the flash card. The majority of users have not reported any problems.
Object
Although the best solution would be a software upgrade to OZ 4.7 allowing users to update their cards, it has been decided to see if by changing the hardware the same result may be achieved. See Writing to Flash Chips for a full explanation of what needs to be fixed. NOTE: This needs to be updated with the results found here.
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| I/O | PIN No | I/O | PIN No | |||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| FROM Z88 SE1 | I | E | 1 | 1 | 0 | 0 | 0 | 0 | FROM Z88 ROE | I | E | 15 | 1 | 0 | 0 | 0 | 0 | |
| FROM Z88 MA19 | I | A0 | 2 | X | 1 | 0 | 1 | 0 | FROM Z88 SE1 | I | A0 | 14 | X | 1 | 0 | 1 | 0 | |
| LOGIC 0 - 0v | I | A1 | 3 | X | 1 | 1 | 0 | 0 | LOGIC 0 - 0v | I | A1 | 13 | X | 1 | 1 | 0 | 0 | |
| TO RAM CE | O | Y0 | 4 | 1 | 1 | 1 | 1 | 0 | TO FLASH ROE_S | O | Y0 | 12 | 1 | 1 | 1 | 1 | 0 | |
| TO FLASH CE | O | Y1 | 5 | 1 | 1 | 1 | 0 | 1 | O | Y1 | 11 | 1 | 1 | 1 | 0 | 1 | ||
| O | Y2 | 6 | 1 | 1 | 0 | 1 | 1 | O | Y2 | 10 | 1 | 1 | 0 | 1 | 1 | |||
| O | Y3 | 7 | 1 | 0 | 1 | 1 | 1 | O | Y3 | 9 | 1 | 0 | 1 | 1 | 1 |
Conclusion
It has been a long journey to get to this point. Further testing will be done before reporting that a hardware solution has been found.
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