EGRET Reverse engineering & reproduction?

mmu_man

mmu_man

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I had some look at the EGRET posts here and elsewhere some time ago… It seems there might be interest in recreating them. I don't really have the need myself, my LC-III works fine for now, but I figured I'd spawn a thread to discuss the issue. The various pinouts don't seem documented yet on the Custom ASIC thread, although the bomarc schematics mostly have them.

I spent some hours digging NXP's legacy MCU catalog, downloading datasheets of similar parts, but I couldn't find one that would work as a drop-in replacement. It seems they shuffled the I/O registers, like port direction and such, so even if it was code-compatible it wouldn't drive the pins properly anyway…
At one point it seems some company did make some more H05 parts, but they don't seem to be available anywhere, and again the datasheets don't give anything directly usable in-place. Unless I missed something…

I guess the solution will be using some other uC like they did for the Amiga keyboard controller which was also an HC05 and they used an ATMEGA.
 
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mmu_man

mmu_man

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Pinout for the uC is in the datasheet, page 81. As for the use in macs, only the bomarc schematics seem to have them.

Oh dear, I went again down the rabbit (eh, appropriate time) hole of digging the datasheets… It seemed like the 68HC705E6 could have been used as replacement, except the SOIC pinout is different, because why not. The other option would be to use the PLCC to have all the required ports, but it's too big.

I think we should first disassemble these properly to figure out which features are used or not.

For the record, see also these threads:

CUDA, EGRET, HC6805 Hacking

I am starting a thread over here, so that Powermax and I stop hijacking the "Q700 ADB or board kaput" thread. This thread is for discussion of topics related to recreating the CUDA and/or EGRET chips from non-Apple hardware. The chips are based on the Motorola 68HC05 microcontroller according...
68kmla.org 68kmla.org

LC575 Cuda/Egret chip

I have an LC575 board that I sent to the great Bruce Rayne here in Australia to repair for me that suddenly died in the Colour Classic I had it in. After a fair amount of troubleshooting he's let me know that it's the cuda/egret chip that's at fault and that he doesn't have a spare board to...
68kmla.org 68kmla.org
 
jajan547

jajan547

Active Tinkerer
Mar 25, 2022
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North Carolina, USA
mmu_man said:
Pinout for the uC is in the datasheet, page 81. As for the use in macs, only the bomarc schematics seem to have them.

Oh dear, I went again down the rabbit (eh, appropriate time) hole of digging the datasheets… It seemed like the 68HC705E6 could have been used as replacement, except the SOIC pinout is different, because why not. The other option would be to use the PLCC to have all the required ports, but it's too big.

I think we should first disassemble these properly to figure out which features are used or not.

For the record, see also these threads:

CUDA, EGRET, HC6805 Hacking

I am starting a thread over here, so that Powermax and I stop hijacking the "Q700 ADB or board kaput" thread. This thread is for discussion of topics related to recreating the CUDA and/or EGRET chips from non-Apple hardware. The chips are based on the Motorola 68HC05 microcontroller according...
68kmla.org 68kmla.org

LC575 Cuda/Egret chip

I have an LC575 board that I sent to the great Bruce Rayne here in Australia to repair for me that suddenly died in the Colour Classic I had it in. After a fair amount of troubleshooting he's let me know that it's the cuda/egret chip that's at fault and that he doesn't have a spare board to...
68kmla.org 68kmla.org
Click to expand...
I looked at some of these, very interesting, I was thinking maybe order a plcc and program it and make a weird adapter, any ideas?
 
mmu_man

mmu_man

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The problem with PLCC is size, there are other stuff around the chip…

I started documenting the pinouts here. I don't see much of the "scrambled pinout" really, power and oscillator pins are still in the same place for what I've seen…
 
jajan547

jajan547

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Mar 25, 2022
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mmu_man said:
The problem with PLCC is size, there are other stuff around the chip…

I started documenting the pinouts here. I don't see much of the "scrambled pinout" really, power and oscillator pins are still in the same place for what I've seen…
Click to expand...
Here’s an LC EGRET pinout, someone else made it already but I can think of any chips off the top of my head that will work. Any ideas?
 

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mmu_man

mmu_man

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Yes that's @max1zzz 's schematics from reversing the board, which just confirms the other ones. Again, while different versions used some GPIOs for different purposes, there is no "scrambling" of the pins with respect to the regular 65HC05E1, it's just that they started manufacturing masked version under their own references with each version and a different use of the I/O pins, but the other pins (power, clock…) are all at the same exact place each time.
So one just needs to flash the correct firmware in a compatible chip to get each version of them.
 
jajan547

jajan547

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Mar 25, 2022
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mmu_man said:
Yes that's @max1zzz 's schematics from reversing the board, which just confirms the other ones. Again, while different versions used some GPIOs for different purposes, there is no "scrambling" of the pins with respect to the regular 65HC05E1, it's just that they started manufacturing masked version under their own references with each version and a different use of the I/O pins, but the other pins (power, clock…) are all at the same exact place each time.
So one just needs to flash the correct firmware in a compatible chip to get each version of them.
Click to expand...
Did you manage to find any chips that have similar pinouts or none so far, awesome work you have done here.
 
mmu_man

mmu_man

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Well there's an OTP version of the HC05E1 (68HC705E1DW, in SOIC package it's only available in OTP) that might still be available in a few places, but I don't know for how much, and when they say "pulled from devices" I'm not what they are worth if they are already programmed with something else…
There's another reference I found that might be still compatible and may be available but I haven't investigated either yet.

Programming them is not that hard actually, their internal bootstrap ROM just needs a programming voltage and will just fetch each byte from a EPROM or another source in sequence. Just need to find chips that are still blank.
 
jajan547

jajan547

Active Tinkerer
Mar 25, 2022
732
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North Carolina, USA
mmu_man said:
Well there's an OTP version of the HC05E1 (68HC705E1DW, in SOIC package it's only available in OTP) that might still be available in a few places, but I don't know for how much, and when they say "pulled from devices" I'm not what they are worth if they are already programmed with something else…
There's another reference I found that might be still compatible and may be available but I haven't investigated either yet.

Programming them is not that hard actually, their internal bootstrap ROM just needs a programming voltage and will just fetch each byte from a EPROM or another source in sequence. Just need to find chips that are still blank.
Click to expand...
Didn’t these types of chips need a special programmer?
 
mmu_man

mmu_man

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jajan547 said:
Didn’t these types of chips need a special programmer?
Click to expand...
Yes and no. Yes, because you can't use an EPROM programmer unless it specifically supports these chips. No because as I said, the bootstrap ROM makes it not so hard to program them with a simple circuit (basically a 12bit counter and an EPROM that you programmed with the code). It's even described in the datasheet.
 
jajan547

jajan547

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Mar 25, 2022
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mmu_man said:
Yes and no. Yes, because you can't use an EPROM programmer unless it specifically supports these chips. No because as I said, the bootstrap ROM makes it not so hard to program them with a simple circuit (basically a 12bit counter and an EPROM that you programmed with the code). It's even described in the datasheet.
Click to expand...
I see, well I’ll try and locate said chips.
 
jajan547

jajan547

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Mar 25, 2022
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Would this programmer work you suppose? The TL866ii Plus I have doesn't support the 68HC05's, I do have 3 spare fully desoldered EGRETs coming in the mail. When these arrive I can try and see if it can autodetect a compatible chip but no promises.
 
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