JECS for “Japan Electrical Control Systems” was also know as UNISIA JECS manufactured many ECU for Nissan, following two ECU, left came from a Nissan 200sx S14a and right from a Nissan Primera P11GT, both cars share almost the “same” Nissan’s SR20 engine, one is N/A and the other one is turbocharged, one is mechanically distributing the sparks and the other do it electronically and there is much more differences between them but pay attention between this two ECU… they are as identical as the engines are: a common basis with some variants.
Let’s focus on the 200sx S14a ECU, here is whats you can find inside: MCU A wonderful Mitsubishi MELPS 7700 MCU (M37780STJ) I have the original datasheet (in Japanese, never translated in any other languages) if your are interested feel free to contact-me.
RAM/ROM IC The ROM is OTP, the firmware is burned once and can’t be modified but the ROM can be disabled while the RAM is still accessible, allowing external ROM/EEPROM/FLASH. The chip also provides memory mapped digital I/O with PWM/Counter capabilities.
Memory bus I don’t know the orignal purpose to let this memory bus so easily accessible. Probably they designed the ECU not only for the final application but also for the engine tuning during the development phase. Because you can easily disable the ROM of the RAM/ROM IC and attach any memory (ROM/EEPROM/FLASH) or also a memory emulator on the memory bus, this is the most probable hypothesis.
Here is the pinout:
I/O Extender Also memory mapped, this chip provide additional digital I/O but not as complex as the RAM/ROM IC, decaping and DIE inspection for identification is planned.
Following is the pinout I found on the Primera P11GT ECU, may vary from one ECU to other.
ASIC When your car smokes like VW diesel with all dashboard’s warning lights on and without the ability to rev the engine… this is the limp-mode. It’s supposed to let you drive to the next workshop. This chip takes the control of your engine in place of the MCU, the control law is as simple as possible with a safe setup for the engine, rev is limited, more fuel are injected than necessary to protected the engine for knocking and overheating, etc. Limp-mode kicks-in when the MCU fail (reset, infinite loop, corrupted memory, unstable voltage, etc.). Back in time memory and MCU aren’t considered safe enough to let them alone in a ECU, an hardened control logic burnt directly on the silicium is considered bullet-proof.
Knock sensor board Knock sensor is nothing more than a simple microphone, this board is filtering this signal with a band-pass filter, instead of using regular FR4 substrat they used a ceramic like substrat more stable and repeatable for impedance controlled trace. Resistor are printed with a special conductive ink for higher value precision. Because the knock frequency vary according to the cylinder bore, the filter have to be fine tuned to only take in account the knock.
NATS memory board NATS for “Nissan Anti-Theft System” can be found everywhere but Japan, this board host a serial eeprom memory to store the rolling code.
The 8-pin IC is a serial EEPROM, see the “N” logo ? It’s from “National semiconductor” maybe a NM93C46, here is the pinout:
Nissan NATS serial memory
Watchdog board This is where the ECU voltage (for MCU, memory etc.) is monitored and also the activity of the MCU, the MCU toggle a pin connected to this board causing a counter reset, if the MCU hang somewhere and “forget” to reset the watchdog counter then the watchdog force the MCU to reset, number of reset are limited and after that the ASIC takes the control over the MCU.
The JECS “A12-281001” is found in Nissan Primera P11GT and seems to be identical to the JECS “A12-280 000” found in Nissan Silvia 200sx S14a but with a different firmware. Because of the memory technology used for the ROM (OTP) the firmware can only be written once, the chip is labelled with an ID identifying the firmware but the hardware is perfectly identical.
Used with the same processor but for earlier Nissan Primera/Silvia the M6M72561J IC made by Mitsubishi looks physically identical, the pinout is also compatible but not the ROM size, the M6M72561J is 32K ROM long and the A12-28xxxx is 48K ROM long. I contacted Renesas (Hitachi, Mitsubishi & NEC) to ask if Mitsubishi made an IC with larger ROM memory but they didn’t.
As you can see there isn’t any logo or clue about who made the chip, I found the memory mapping by analyzing the firmware but still didn’t know who made the chip !
This chip is more than a simple ROM memory, there is also a RAM bank and memory mapped digital I/Os counter and PWM capable. It’s an all-in-one memory and I/O expander.
The only one solution is DIE inspection but to access to the DIE first I have the decap the IC. Laser helps me a bit but the nitric acid was more helpful (but takes more time)
Unfortunately the IC is damaged (pin, bounding, etc.) but not the DIE and here is what I found: Please read “NEC” not “NFC”, so it’s a NEC IC potentially named D29501 ! Thanks to my amscope metallurgical microscope !
My laser cutter is now cutting, thanks to all the improvements I made (head, power bed, power supply, controller, …).
Now I want to add a galvoscanner to my laser cutter head to raster IC for DIE inspection, galvo motor are expensive and because many people build them from almost anything with a coil (speaker, fan, hard-drive, etc.) I decided to also built one by myself !
I used FreeCAD (0.15) to drawn all parts and also check if the assembly will work, here is a partial assembly of my experimental galvo bench:
I design two coil holders disposed at 135°, in this configuration I’m supposed to be able to rotate the mirror from 0° to 45°, keep in mind it’s for experimentation so the travel angle is large to see any influence of magnetic field variation.
All parts were exported to DXF files and then assembled with QCAD, thanks to QCAD customizable CAM export for generating GCODE compatible with smoothieboard.
Here is the result of the laser cutting:
3mm thick plexiglas (or supposed to be because it smell a bit like chlore when cutting), with 300mm/mn and 6~7mA and laser focus 1mm underside the top surface. Only one pass was necessary and the result is great !
Here is the assembled experimental bench:
Of cour coils are missing, this is for the next step, keep in touch !
You just bought a K40 chinese laser cutter ? Unfortunately it’s merely impossible to cut anything with the stock laser head because of the fume spreading the laser beam and stain the less reducing the power.
Here is the solution, LightObject.com made this nice laser head:
Delivered without the lens because stock lens doesn’t fit with. This new laser head is made for 18mm lens, stock mirror can be reused (same size).
Here are all the parts, assembly is easy and fast:
I also ordered a standard 18mm lens:
Overview of all the parts:
As said, assembly is easy and fast:
Combined with the power-table I can now cut almost anything ! No more dirty lens !
I bought a 40W CO² laser from ebay but wasn’t satisfied with for many reason, one of them was the bed, stock bed cannot be lowered even manually. I was also looking for a new laser head with air-assist when I found this power table/bed.
LightObject.com sell a lot of parts for laser and CNC and today I will talk about this nice product through a step-by-step assembly, here is all delivered parts:
Let’s start the assembly with the lower frame and the four threaded-rod, simply insert the bearing in the frame:
Insert the four axis:
Remove the bearing and the upper lock nut:
Turn all the four nut:
Pre-install the belt and the stepper:
Fasten the stepper with the two screw:
Install the belt-tensioner, with light tension as long as the assembly isn’t done:
Install the bed (and the lock nut):
We removed the bearing from threaded rod, now it’s time to install them in the upper frame by gently pushing them in the blind hole, if it’s hard to insert try another bearing/blind-hole combinaison, never use a hammer !
The upper frame can now take place, don’t forget the previously removed lock nut. Simply insert the threaded rod in the bearing:
Fasten the upper frame with screw:
Almost done, you can now adjust the belt tensioner:
Flip the power-table upside down:
The lock nut is in contact with the upper frame and the bed lay on the four lock nut, it’s now time to lock them all:
And it’s done !
A pleasant hour long is required for the assembly but if you don’t take photography it’s done in less a half-hour !
Here is my power-table in place in my K40 CO² laser (I painted it white because the stock blue color give me cancer !)
For my first article I wanted something different, instead of introducing myself I preferred to show you my last tool investment. Tool ? Don’t worry this isn’t an article about screwdriver ! Let me introduce to you the Metallurgical microscope from AmScope, named ME320TWB-PZ-2L-10M, it’s a 40x~2000x metallurgical microscope with a 10 megapixel camera and a couple of filters (one of them is polarizing light).
For what ?
For DIE inscpection ! I have a couple of anonymized ICs, impossible to know whats inside ! I bought a set of nitric acid and acetone and start a chemical decapsulation, with a cheap USB 200x “microscope” I tried to find a DIE marking or something who can help me to identify the original IC. But with cheap tool come also cheap result.
So I decided to invest in a metallurgical microscope, I was first looking on used Nikon, olympus, zeiss, etc. Too expensive even with broken/missing lens… After reading feedbacks from AmScope devices I decided to bought one on Ebay, was also expensive but I was impressed with the overall quality, the quality of the camera, the software (delivered with SDK !), of course lens aren’t ZEISS or Olympus, corner are darker than the center and with highest magnification I noticed rounded corner (picture is no longer flat) but for my application and my budget I’m totally satisfied with.
Here is a combined set of pictures taken with my metallurgical microscope, you can see an overall view of the DIE: