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Main shit - the best the newest and the most realistic - all about DtZ ! :> My computers: Z80,68K, etc :> SD / SDHC Interface for Grant Searle's CP/M computer :>
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The Idea: lets' try to build it.
The Scheme:

The software: here
Note: This is the very first attempt to make it work. In this scheme the interface and software are attached to port 16h (same port as CF interface), but after the initital release I put it on port 8, and all the future software, starting with 2321 release works with it. So instead of U5:13 connect it to U5:14 and reassemble the given source (or just use loader_debug.hex from release files)
The results: at least, SD answers properly to "GO IDLE STATE" command (in the moment of initial writing; currently it works with CP/M)
The note: by a strange reason, Z84C0006 (CMOS one) did not hear open collector (yes, inverted) input (at least in my scheme), SHARP LH0080A does. That was because I had no pull-up resistors (4.7k) on data bus. Install them!
And I used 1K resistors instead of 680 ohm resistors mentioned on scheme - I had no 680 resistors around.

Testing it all:
Plug off SD/MMC, load basic, say
OUT 16,0
Repeat OUT 16,7 and OUT 16, anything and check for triggers
Then, shorten data out line to ground and
Lower bit should be 1 (this is an inverted data)
Leave data NC or plug it somewhere to +5 and repeat, you should get lower bit 0.
If it does not, change CMOS CPU to NMOS.... install pull-up resistors on data bus!

As for CF interface, yes, it was very hard to solder it, and ONCE it even loaded, but I mostly got a strange hang after reading sector $38 (I wrote a debug program showing me how does it loads). I've tried to change all the logic chips to HCT, make my wires shorter - same result.

UPD 20130108: The purpose of the led (that should be a RED led) is to drop voltage from +5 to somewhere from +2.8 to 3.3. I saw this recipe in inet, but I do not remember where. Note: before CS goes down, this led may not be turned on.
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20181231 Long-awaited FAQ
20170103 SBC Atmega8 + RCA1802 / CDP1802 CPU launched
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