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====== ECB SBC Z180 mark IV / mk4 ======

What a wonderful design! Has both SD card and IDE interface onboard, fast and easy to build. I love it!

Tips on U10:\\
I have just learned that when building this with all 74AHCT chips; the U10 (74ls38 NAND BUFFER) can be substituted with 74AHCT00 (NAND GATE), since the specs for the AHCT variant of the '00 exceeds the driving capacity of the '38 by +5mA. (I have not found a single 74AHCT38 for sale anywhere)

U10 has 4 NAND's, but only 3 are used in this design;\\
* U10A=/CS (Card Select of the SD card)\\
* U10B=Activity LED driver\\
* U10C=/INT2 signal to CPU on pin 12.

I have tested it for a week now and it seems to work fine with several SD card types, RomWBW 3.0.1 (with 2 custom config; supercap charge set on and activate PropIO v2 on boot)

I have not tested the MAX3467 / RS-422 yet.

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|Built with 74LS chips and 18.322Mhz 1x CPU clock  |{{https://www.retrobrewcomputers.org/lib/exe/fetch.php?w=400&h=695&tok=891a70&media=https%3A%2F%2Fwww.retrobrewcomputers.org%2Flib%2Fplugins%2Fckgedit%2Ffckeditor%2Fuserfiles%2Fimage%2Fbuilderpages%2Fspeed3ple%2Fimages%2Fimg_20200730_220045small.jpg?400x695|ECB SBC Z180 mk4 with LS}}                           |
|Built with 74AHCT chips and 18.322Mhz 2x CPU clock|{{https://www.retrobrewcomputers.org/lib/exe/fetch.php?w=400&h=904&tok=5dfee9&media=https%3A%2F%2Fwww.retrobrewcomputers.org%2Flib%2Fplugins%2Fckgedit%2Ffckeditor%2Fuserfiles%2Fimage%2Fbuilderpages%2Fspeed3ple%2Fimages%2Fimg_20200730_220036small.jpg?400x904|Z180 mk4 built w AHCT complete with CF and SD cards}}|
|U10 seems to be ok with a 74AHCT00                |{{https://www.retrobrewcomputers.org/lib/exe/fetch.php?w=400&h=534&tok=6bdeca&media=https%3A%2F%2Fwww.retrobrewcomputers.org%2Flib%2Fplugins%2Fckgedit%2Ffckeditor%2Fuserfiles%2Fimage%2Fbuilderpages%2Fspeed3ple%2Fimages%2Fimg_20200730_220430small.jpg?400x534|U10 - 4 NAND buffer}}                                |

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