drembedded

I've been reviewing the $0d_hack.src source code for the 7427. The comments are helpful to understand what the code is doing but it would be even more helpful to known which port I/O digital pins are connect to which pins on the connector that the wiring harness connects to (one long run-on sentence sorry). To put it another way, if I read bit 7 of port A, what pin on the ECM connector is this signal connected to? The same queation goes for the input capture, output compare and analog to digital channels. I have searched through several web sites and have found the pinout for the wiring harness but not what the connections connect to inside of the 68hc11 variant.

For instance, from what I can tell the Output Compare 5 looks like it controls the injectors. As for the Analog to Digital channels:
channel #1->TPS
channel #2->MAP
channel #3->O2

Thanks,
Michael

dimented24x7

iTrader: (2)

Teh A/D looks like its multiplexed. There are LOTS of channels to handle all the inputs. TOC 4/5 and TIC 3 look like they handle the injectors on the CPI/PFI setups. The TIC 3 is tied to the TOC 5 (TOC 4? cant remember) so there can be, at least what appear to be, alternate injector firings for bank fire. If you have TBI, all this is a moot point as the TBI uses the standard drivers that fire with the DRPs. This also probably serves the RFD function for the PCM. The code skips over the CPI code and just writes the pulse width to the hardware. When CPI is in use, the accumulator for the TBI hardware is zero'd out.

As for the TIC/TOC heres what Ive found so far:

The only way Ive found to ID the hardware is through the code. Ive gone through and reversed alot of the code (sans auto trans crap) on teh $OD (spark/fuel loops most of the subroutines/O2 PID loop stuff/EGR code, etc.) and that at least provides some hint as for what does what hardware wise. Ive yet to see any schematics for the PCM. So for the near future, the hardware remains a mystery.

drembedded

Dimented24x7 thanks for the reply. That helps to better explain the vector table.

Although I've been working with 68hc11s for some time(used in satellite dish and LNB controls), I'm new to engine controls and associated initialisms (versus acronyms. You refer to DRPs, CPI, PFI (Port Fuel Injection?), RFD etc. Is there a posting or page I can go to that will explain their meaning?

Thanks,
Michael

dimented24x7

iTrader: (2)

The microcontroller in this appears to be a n HC11F1.

Some helpful terms:

Distributer Reference Pulse, one each time a cylinder fires

Center Port Injection, used on the 4.3's Its a total piece of crap, IMO, and it caused me endless grief with my old blazer.

Redundant Fuel Device, this fires the injectors autonomously in case the microcontroller takes a dump. Id speculate that this + a portion of the injector drivers is the same as what was on the old TBI ecms given that alot of the related hardware and small chunks of code appears to be the same.

Throttle Body Injection, has two injectors that squirt fuel in on top of a throttle body, hence the name.

As far as computers go, you picked the hardest one. The code on the PCM in question is some 6x the size of what was running on the earlier TBI ecms, and 2x the size of the nearest ECM, the 90-92 TPI 7730. This is also one of the nicest HC11 based GM computer made. The MCU is fast, apparently even faster then a standard HC11, and the code has everything imaginable, including PID loops for just about everything. Theres so much there that I cant even remember any of it. It just all bleeds together. Should make tuning the car interesting

drembedded

I'm in the process of putting TBI on a SBC in an older CJ5. I've got a 1227747 but some have suggested that the 7427 would be a better unit. Sometimes better means harder as well AND more rewarding!

One more question for you(well a couple of questions on the same topic). The code is written using a "run to completion" model driven by interrupts. I've seen comments about major loop and minor loop. Does the code follow a major loop with minor loops in between? What do each of these loops accomplish?

dimented24x7

iTrader: (2)

Not too familiar with alot of the terminology, but Id say pretty much that, or maybe round robbin is a better description, but not to the extent that the earlier computers where. There is the main vector handler which runs the fuel, spark, and transmission main routines, which in turn have their own subroutines, which in turn, again, have their own subroutines.

Basically the main vector handler runs at 160 Hz. The spark and fuel routines are run on alternate passes at 80 Hz, then there are others run at 40 and 20 Hz, the trans stuff is intermingled here and there in these loops, and there are 16 subroutines executed in the main vector handler that are run at 10 Hz, one routine each pass.

Many of the routines have subroutines nested within them. Much of the PID loops are nested within the subroutines, and executed on alternate passes at varying frequencies in a staggered pattern to help optimize the execution time available. The whole thing gets sort of hairy

In addition to this, there are alot of routines that are driven by inputs/TOC's only and run as needed and at any time. The DRP routine that handles the interrupt injector firings is a good example. Run every time a cylinder fires and a DRP comes in.

In contrast, the older TBI ECMs have everything on a fixed schedule. The vector handler executes the main fuel routine or spark routine, and one of the 10 Hz routines each pass. Rinse, repeat as they say.

dimented24x7

iTrader: (2)

Now taht I think of it all that slicing and dicing is how they probably stuffed it all in there. The MCU probably is no faster then the previous ones used in the ECMs. The code reminds me of a fractal, with many smaller bits attached to the larger ones.

Grumpy

Just hang on, and wait for the Ultimate TBI stuff to ge released. It's hands down better then anything GM's put together for a TBI, IMO.

HaulnA$$

I'll second that. This is a nice piece of hardware with a complex code set which makes it a tough nut to crack, but it also makes for a ton of interesting possibilities.
This may be a better idea for the Jeep project especially if you are not going to run an electronically controlled tranny. All the hard work has already been done. JMHO

dimented24x7

iTrader: (2)

The U-TBI code is nice, no doubt, and a great thing for the tbi community, and would be a better choice to get up and running.

On the ecm/pcm side, though, there are some advantages that the PCM will always have over the earlier C3 based systems. First, obviously, the MCU is faster and more capible. One thing which I really like is the I/FDIV instruction pair. These allow for the SD calcs to be actual equations with real everyday values like air density, cylinder volume, etc. rather then table lookups. Helps to preserve accuracy. The other things that I like are the closed loop derivative spark/fuel rpm control routines that also work with the O2 PID loop to control the idle. There is also closed loop derivative control thats active when a manual transmission is present. This means the possibility of reduced or no bucking/surging even if a less then optimal tune is present. With all this code, its engineers gone wild! Theres lots of stuff in this thing. The transmission code wasnt the only thing added, all the routines where greatly expanded and improved.

As for the PCM, theres lots of possibilites. It has all those extra inputs, TICs, and TOCs that no other ECM has. Those are very powerful tools. There is also an interrupt each time a DRP is present. To me, that opens the possibility of a fast WB-O2 PID loop that runs in step with the motor and can use proportional and derivative terms as its primary form of control rather then just the integrator. Lord knows all that CPI crap takes up enough time for it. The PCM is quite complicated, but if you can master it, you wield the mightiest 8-bit sword there is

Grumpy

You can run all the processor, you want, but if the code is lacking, the processor can't make up for that. You can speculate all you want, but like I said:
**
It's hands down better then anything GM's put together for a TBI, IMO.
**


Toss in the Lockers for it, and there's nothing even remotely close to the U TBI.

Using just one element of the U TBI in my 7060, gave me a 1+ increase in MPG. When released I'm going to use a U TBI instead of my 7060 for engine management, and the 7060 just as the tranny controller.

Using the U TBI, Lockers, Ostrich, gives you more then any other system available, real time emulation, scanning, and the best code available.

Anyone's free to speculate, but, it's still just speculation, and may or may not have much to do with the actual facts. Processor power, and eye candy haven't a thing in the world to do with actual results, it's all about the code. If someone wants to rewrite another PCMs code, they might approach the U TBI. Like I said, I've run just one portion of it, and there is just no comparison about it, to the oem GM code.

dimented24x7

iTrader: (2)

I wasnt speculating on RBobs code. Having used and programmed on the C3, I know that it has its fundamental limitations which cant be overcome, which is why I put it down, and decided to move on to something better. Its a great computer for what it is, but its somewhat confining, and requires one to make trade-offs.

As for the code, again, I cant speak for RBob, but alot of the add-on routines that I put in that seemed so novel, well, werent... These same routines apear in the later code. Reason being is that with all this code, form follows function. Also lets not forget that these where engineers, not pre-schoolers and teh code serves a purpose. The first ECMs made where from a time when all this was new and untried, and the computers where primitive. Fast forward 15 years, and alot more is known about engine management, PID control, etc. AND it shows. We can point and say how crappy the early TBI code was on the first ecms, but at that time they where breaking new ground. I dont know about you, but Id be pretty damn clueless as an engineer with this new fangled computer instead of a carb sitting in front of me back in the late 70's or so. As they say, hind sight is 20/20.

Lasty, as there is no actual commented hac for the P6 stuff, so you are speculating as well The 'hac' actually really just points out the constants and maybe draws some parallels to the previous P4/C3 ecms. The calibration section came from another source Most of what Ive encountered is all new and previously unknown.

va454ss

iTrader: (1)

Well, that helps me make my decision about staying with the 7060..............

drembedded

Thats quite a bit of information to internalize. It should keep me busy in reviewing the code.

As for the "Ultimate TBI stuff", you've got my attention. What is the "Ultimate TBI stuff"? Is it based on an OEM computer or is it something like megasquirt, etc.? Who is doing the work?

dimented24x7

iTrader: (2)

RBob can probably tell you more as its his baby. The UTBI is a project that replaces the stock TBI code on the older 6809 based C3 with revised code and a board that expands the addresable rom space, adds high speed transmission of all 256 bytes of memory, provides extra inputs, has a nice user interface, and works with eprom emulation, or so I gather. It sounds really nice and Ill probably try it out. Do a search in this forum. Theres a whole thread on it.

I went down a similar road. I went romless and converted the entire code on the C3 into basically a computerized holley carbeurator and vac advance dist. using a 3.5" LS1 MAF. It workedjust like a carb. Sort of primitive but you could just slap it on, start up the car, and drive away. Not much tuning required. The thing that annoyed me was that the MCU could only run so much code so I was limited with what I could do and the hardware was too basic. I guess thats to be expected, though, with a 20 some odd year old computer.