YarnMaster
ANyone know anything about micro controllers????
Have just opened up my spare EAS ECU to see what micro controls it.
Processor is a Motorola made MC68HC705B5CFN.
My bug is with the inability to clear a fault in the EAS without going thru Testbook or a reading module of somekind.
What I would like to know if there is a way that the programming can be read from it and altered or if there is some way of externally initiating a reset that will clear the code fault, OR disabling the fault coding in some way.
I have d/loaded the data sheet for this micro and will gladly pass it on if someone has the ability to do this.
Have recorded pressure switch faults on the last 3 Testbook readings and replaced the switch yesterday, but again today have recorded another fault which I still have to get confirmed, but I will put money on the fact it is another switch fault "not changing state, always on" which I am presuming means it is always open and keeping the compressor on, although it does seem to switch on and off.
Ran fine yesterday and today until this afternoon when again I started the car and the lights came up flashing again.
Having a quick look at the factory manual shows a 1Kohm resistor inline with the switch, in the harness so I am going to check to see if this is maybe faulty and not allowing the ECU to see the switch close all the time to cut off the compressor, but if anyone wants a little project, then this may be it.
Everyone says to me "Why dont you just put coils in it?" My answer is "I will not admit defeat and I like the air suspension, just not the cost involved to reset the f*****g thing all the time!"
My feeling is that there is a lot of people who dont understand it properly and I have spent alot of time understanding the ins and outs of it and how to read and dignose the faults as in most cases the fault given is caused by a number of different factors.
As a fair part of my career prior to the engine game was diagnosing faults in pneumatic systems, hydraulic systems, some of which are linked to or controlled by electrics etc, it becomes a determination NOT to be beaten by the idiot who did a half assed job at designing this thing in the first place and looking for a way to make life easier for everyone that has one and bring confidence back to a misunderstood product.
Cheers
Andrew
ChatterBox
Swaggie
As you have the datasheet, I assume you have the pinouts and can see pin 6 is the reset pin. On Picaxe ICs, connecting reset to gnd clears program memory (but not the program) and restarts the program, but have no idea if the same applies to this IC.
Edit: you could possibly clear vital program parameters and make it unuseable!
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Master
I used to sell these components to engineers.
Not Motorola stuff but National Semiconductor, Zilog, Fairchild, and few others!
I would suggest contacting Motorola in the State's and quizzing them directly.
Motorola "...HC..." gear drives most of the World's fax, copier, etc. items.
Could be worth the trouble.
Edit: I know Moto. are not U.S. From experience, it is usually where you get the best response!
YarnMaster
Yep I know all about the reset pin, but as you stated as the prog code is unknown, it may well wipe something I dont want to hence my query for someone sliiiiiiighty more experienced than me!!Originally Posted by Graeme
Here is the datasheet anyway, have a peruse and see what you think! Had to Winrar it as the pdf was too big to upload here.
The thing I am unsure about is that AFAIK to reset any faults, its usually a flash write thru the comm port so whether or not the reset pin works is a mystery!
Cheers
Andrew
Fossicker
I just finished a microcontroller course. The only safe thing to do is read up on the data sheets or contatct Motorola like recommended earlier. It should just reset and clear faults, but not worth the chance of it clearing everything to a factory setting.
When in doubt read the manual.
TopicToaster
iaw Motorola identification
the "7" signifies an EPROM or OTPROM and not EEPROM. It is therefore not electronically eraseable. A reset will not result in an overwrite of the EPROM. But I don't think a reset will do anything that turning the power off the unit wouldn't do.
Most of the sensors connected to the micro are likely to present high or low impedance which you should be able to establish by placing a meter onto the sensor. I doubt that the problem is going to be antwhere else other than the sensors or the connection to the same.
good luck
YarnMaster
I checked the pressure switch operation of both the old and new one and both work.
I also checked the line resistance from the switch back to the ECU plug and it came up exactly 1kohm as per the schematic in the manual and checking the switch operation plugged into the harness also came up fine.
My only guess now is that maybe the pump isnt reaching the cutoff pressure or its not getting there quick enough and is leaking back through the seals under compression.
Got the fittings to connect up a schrader valve and pressure guage to the tank so I can check how quick the compressor takes to fill from empty.
Might use the spare as a sacrificial as this has a fault in it anyway and a try to reset it could at worst result in me turning the box into a manual test unit!!
Used to use a particular EPROM with the window for UV erase for control equipment back in my hydraulic control days. I would assume the one in the ECU is an OTP as they are a micro, not dedicated EPROM. But it couldnt hurt.the "7" signifies an EPROM or OTPROM and not EEPROM. It is therefore not electronically eraseable. A reset will not result in an overwrite of the EPROM. But I don't think a reset will do anything that turning the power off the unit wouldn't do.
YarnMaster
Just had a head f**k reading thru the datasheet but did come across this.
The MC68HC705B5 is a device similar to the MC68HC05B6, but with the 6 kbytes ROM and 256 bytes EEPROM replaced by a single EPROM array. In addition, the self-check routines available on the MC68HC05B6 are replaced by bootstrap firmware. The MC68HC705B5 is intended to operate as a one time programmable (OTP) version of the MC68HC05B6 or the MC68HC05B4,
meaning that the application program can never be erased once it has been loaded into the EPROM. The entire MC68HC05B6 data sheet applies to the MC68HC705B5, with the exceptions outlined in this appendix.
Features
• 6206 bytes EPROM (including 14 bytes User vectors)
• No EEPROM
• Bootstrap firmware
• Simultaneous programming of up to 4 bytes
• Data protection for program code
• Optional pull-down resistors on port B and port C
• Additional temperature range available; -40 to +105¡C
• MC68HC05B6 mask options are programmable using control bits held in the options register
Si I guess its back to the drawing board!!
TopicToaster
The reference to the type of memory is for the part that holds the code, a lot of controllers come with an amount of onboard memory to avoid having to have seperate micro, EPROM, interface chips etc, etc.
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