Or maybe somebody has an even brighter idea how to solve this? Also there might be a chance the M0 gets stalled by activities of the M4 on the shared bus matrix. The M0 runs at 100MHz so you can tolerate 9 instructions, but I cannot find how fast the GPIO registers and SRAM are. However, I am not sure whether the <90ns access time can be guaranteed by design. Then write some assembly code for the Cortex-M0 to emulate the EPROM. Anything against this approach? Any comments on the MCU / CPLD / Memory choice? Also I was thinking about a simpler / lower cost solution, using a dual-core MCU like the NXP LPC54114.
As a later step I can improve the VHDL / Software and ditch one of the two SRAM chips. However, for the first version I can just put two of these chips on board and toggle between them (so update one SRAM while the OKI fetches instructions from the other). The SRAM has an access time of 45ns, so I theory it should be possible to write to it between the OKI fetching its instructions. Now I am thinking about the following solution: Using a STM32F0 for the composite USB device and data updating, Lattice MachXO2-256 device and 2x SRAMs like ISSI IS62WV1288DBLL-45QLI. Data updating and USB is provided by a NXP LPC1768. The Hondata hardware uses a Xilinx CPLD together with a SRAM. Data is updated by an ATMega and USB is provided by an FTDI chip. The Moates hardware uses a Xilinx CPLD with an Everspin MRAM. I already looked at the hardware used by Moates and Hondata. If somebody still has the design files I would appreciate it if somebody can send me the files. I have already searched and found the following topic: In the past somebody called "Obeny" also developed a similar device, but unfortunately his website is down. This would be the biggest challenge I think. I would like the emulator to be able to change data while the 66207 keeps running. So what I need to make is a device with a USB plug on one side and a 27C256 EPROM I/F and UART on the other side. The tuning tool supports a few EEPROM emulators, all of which use a serial protocol. The OKI 66207 also uses an UART to send logging information. The OKI 66207 reads the firmware from a 27C256 EEPROM (32kByte). Technical details: The Honda ECU uses an OKI 66207 microcontroller running at 10MHz. So please do not comment I can just buy something of the shelve: this project is for educational/entertainment purpose. I was thinking of building my own EEPROM emulator, because I want to refresh my PCB / SW / HW knowledge a bit. You can buy the Moates Demon/Ostrich or the Hondata S300, but these cost well over 200$. To solve this there are quite a few EEPROM emulators which allow live updates to the emulated EEPROM for a PC.
This is a cumbersome process as with every change you need to stop the car and update the EEPROM. Recently I have been tuning a Honda car with an EEPROM burner.
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