VR memcal EPROM settings

[vlad01]

yep, 100ns probably will work but might be a bit flaky and cause the ECU to hang randomly.

[The1]

i recall vl400 doing testing, over 120ns isn't recommended, early nvrams were 120ns from memory. All new chips now we use are 70ns, most of the factory chips are 120ns, even the Flash PCM's use 120ns

[j_ds_au]

Do we know the MCU clock frequency/frequencies (or crystal/s) used in the various ECU/PCM? This can be used to work out the required access speed.

The 1227165 has a 2.097MHz MCU clock (8.388MHz crystal), but I don't know if the 1227808 follows suit. I think some later PCM run at twice this speed, but I'm not sure. Perhaps someone here may know.

Joe.

[vlad01]

i recall vl400 doing testing, over 120ns isn't recommended, early nvrams were 120ns from memory. All new chips now we use are 70ns, most of the factory chips are 120ns, even the Flash PCM's use 120ns

I thought the factory ones were 90ns ? and that 120 was the upper most limit but wasn't reliable at that slow speed.

[antus]

the 165 and the 808 are the same, the only difference is the SXR chip for ALDL (and a resistor thats part of that)

[j_ds_au]

OK then, taking the MC68HC11F1 specifications and a 10ns margin, we get :

MCU @ 2.097MHz : 250ns
MCU @ 4.194MHz : 90ns

These numbers only apply for similar MCU's in the 68HC11 family.

So for the 1227808, the access time needs to be 250ns or better.

Joe.

PS. See update below re. MCU speeds.

[antus]

Yes, and that may be right but its theoretical and not recommended. Faster chips are the norm and quite easy to find and the price difference isnt much if anything so i would still keep it down around 100 or lower. I wouldnt feel confident going that slow without some serious testing (im concerned about switching times and vl400 did report problems at speeds that slow).

[delcowizzid]

yeah 120 or faster is the go wouldnt go any slower

[j_ds_au]

yeah 120 or faster is the go wouldnt go any slower

Sorry, but 120ns doesn't correspond to anything. It's way plenty fast for a 2.1MHz MCU but too slow for a 4.2MHz one. You may also need to specify which ECU/PCM you're referring to, because they may not all run the same MCU speed.

As for the 1227808, I have confirmed that indeed, this runs the same MCU speed as the 1227165. Therefore 2.097MHz, therefore 250ns or better for the EPROM (as based on the 68HC11F1 spec's and a 10ns margin). From factory, I have seen an '808 with a 150ns EPROM, so that confirms 120ns is not a relevant number here.

As for other 68HC11-based ECU/PCM, if they run the MCU at 4.2MHz, they need 90ns or better (for a 10ns margin). 120ns would be too slow, 100ns would be pushing things.

Joe.

[hoopstar]

So at which model/service number did Holden switch to 4.2Mhz?