Hello, This email message is a notification to let you know that a file has been uploaded to the Files area of the FM900 group. File : /FM92reverse.zip ...
FM900@yahoogroups.com
Dec 7, 2008 11:00 pm
6646
Sorry for the delay Jason. It has been 10 years since I worked on this project, I still have the info, but it was not easy to find. I have uploaded...
Hi Barry, This looks like a real treasure trove of stuff for the '92 - especially the .asm code! Many Thanks! Mark vk3byy ... From: FM900@yahoogroups.com...
Hi Barry, Thanks for that, I'll be giving it my best shot in the not to distant future, and I'll post my results as a go along, hopefully it'll be a one shot...
Yes, and they are cheaper from certain mail order companies that a real 27C64! By using a 28C64 instead of the 2764 it may even be possible to modify the '900...
Hi Ron, I have been having a go at modding the Bin file, please bare in mind I have had only a little bit of experiance with this sort of programming in the...
Jason, You have it all correct. The A and B band instruction just means that the hardware is physically A band (the radio is FM92A) but you tell FPP that the...
Just a note on checksums. The way ranger_4740 used works but is a bit complicated. The checksum at $1f64 is not calculated on the entire bin file but only...
Ron, You are quite correct the range checked is $0100 to $1fff. However I had noted what appears to be a byte in the first $ff bytes that adjusts the checksum...
Hmmm! That's interesting what you say Barry about the first $ff bytes and the checksum in there. I think you are referring to the byte at $22. Once I...
I don't think they were trying to protect anything - otherwise they would have used a much more obscure checksum algorithm. The self modifying code was...
Mark By use of the word "protect" I was referring to protecting the data not so much Mr. Philip's property. You are quite correct in that they could have used...
Hi Team I've been experimenting with this over the last few days, and managed to get it working FB. Thanks Barry for your efforts and Ron for the checksum...
The problem with the possible checksum at $22 is that I think it can be anywhere in the first $ff bytes. I moved it in my modified EPROM to $1f. I believe it ...
Barry I suspect you are correct about the byte at $22, it can be anywhere in the first $ff bytes. This would make sense. This checksum cannot be used by the...
Hi there John, now let me see if I can help, and not lead you down the garden path, what I did was using hex workshop as suggested by Barry I selected the...
He is ALIVE. What happend to you, fell off the edge of the world or somthing?? Cheers Paul VK2EX Merry Christmas old fella ________________________________ ...
... Well, thanks to Barry's gem, I have been sOOOOOOoooooooo bizzy learning about Hex editing and FM900 eprom programming, that everything else has been put on...
... Howdy Jason That's exactly what I did, then realised that the resulting $FF checksum value using $79 was only out by $01, so upped the patch value by that...
Remember that the checksum in THIS position must add up to $00 so, $00 - $86 = $ffffffff7A or in 8 bit form $7A On my calculator it is neater to use $100 -$86...
... Figured it. 8 bit number has 256 possible values, so subtract from 256 ($0100) instead of $FF which is 255. Simple arithmetic after all ;-) Cheers, John --...
... Got it Barry! Thanks. And just LOVE the flashing red light the FM92 gives on repeater reverse. What a neat trick for such a useful facility. Cheers, John ...
OK, so lets see if I've got this right: If you add all the bytes from $0000 - $00ff you should get an 8-bit sum of $00. This checksum isn't checked by the...
Mark I believe what you say is correct. To illustrate this here is the routine from my checksum program which does the 1F64 calculation. It is written in...
Ron, I took your experiment to the next step and I believe we have an answer. I generated two files with FPP, one with the master file altered and compared...
Barry Yes, I didn't go that far. But that looks like the answer. I am sure the bin file would not run with this change as the checksum for $100 to $1ff would...
BTW - Adding all the bytes together seems to be a fairly common method for calculating checksums in EPROM programmer equipment. The software that drives my...
Thanks all for this wonderful information, I now see my simple error, I started my calculation at 1 instead of 0 DOH!!! Now just to find my cordless...
... The story goes that they had a hard disk crash at Philips TMC and lost all the source code, and when they went to get the backup tape they found someone...
Having problems with message search?
Fill out this form to ensure your group is one of the first to be migrated to the new message search system.
