RomRaider

Hi. Anyone tried to read it in programmer mode? Emulates 32pin eprom 28F101.
Diagram from datasheet:

Preparing for MCU desolder. I have to make and order pcb, to make wires soldering more easy. Work in progress...

MCU was desoldered and placed on paper with printed pcb. Pads dimensions is correct.
PCB will be ordered after new year holidays.

PCB's arrived from China factory. Need more time for experiments )

MCU was soldered on board. But reading is unstable. Seems it resets over time and dump is broken.



I think problem in power-on reset circuit. Can't find it in datasheet. I used analog circuit instead.



Anybody knows what values of C1 & R1 should be used?

It looks like a decoupling capacitor is installed too far from the chip.
I am afraid more capacitors are required to be mounted near the chip.

You may try to increase the power voltage a bit and to use lower clock frequency for the programmer if possible.

Thank you for advice! I will try it)

I'm surprised you can get it responding at all. There really ought to be a set of decoupling capacitors directly adjacent to every set of VCC/GND pins (probably 2-3 per set of VCC/VDD pins, so ideally around 40-60 total capacitors) around the chip on the PCB. If you're good with a soldering iron, try soldering some small caps directly on top of any adjacent VCC/GND pins on the chip... I don't know the pin pitch for that chip, but I suspect you'll be limited to either 0201 or 0402 size capacitors.

As Sasha mentioned, you can also try lowering the programmer frequency as much as possible.

I'm using MiniPro TL866II Plus programmer. Frequency and voltage change not possible for this types of eprom.
I will try add more capacitors and write back.

You may power SH7051 externally.
Moreover your programmer may be not ready to provide the power supply current required by SH7051.
You may try to use the oscillator crystal with lower frequency to decrease power consumption if this does matter.
Verify SH7051 power voltage while reading.

Tried with external power. Voltage always 5.2V. But with external power i have to do manual reset, every time before reading.
But nothing changes. Peaces from beginning of rom shown in other places. And reading every time is different.
Messed rom attached.

The other question is if there are supposed to be any impedance-controlled traces for comms between the SH7051 and the programmer, and if so, did you design the PCB accordingly?

Maybe for XTAL pads it's needed. I don't know.

By the way, in programmer software i have to choose AMD AM28F020 instead of Hitachi 28F101P, as written in datasheet. Because 28F101P have half of ROM capacity.

Did you read it same way or via SSM?

I am too lazy to resolder a couple of dozens of chips to get the technology ready...
Those ecu's are not as widespread as Toyota's where any expenses for hacking are reasonable.

You have a problem with the address bus data.