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Dear Friends: I designed a gas pump which used an MC68SEC711E9. This was, by that time, the only HC11E chip that had a security bit and it was very hard to get and also very expensive.The security feature and the way it works was a mistery for a long time. There was a very poor explanation about this issue in the E family pink manual. The second ( and thicker ) version of the E family manual was equally confusing. If you want to really know how it works, you should take a look to the bootstrap monitor listings at the end of the pink manuals. I believe that the generic HC11 pink manual also talked about security in these devices but the real thing is to study the assembler of the bootstrap code. The SEC chips completely erase RAM and EEPROM when the security bit is active and the chip comes out of reset in bootstrap, expanded or special test modes. The code inside the EPROM can be perfectly accessed at all times, so Motorola explains that the "security" feature is achieved, for example, by storing an array of pointers to functions in EEPROM, so the main program can call these functions invoking the pointers indirectly. In assembler terms, you can call some routines by first loading the address of the routine in the index register and then do a JMP 0,X or JMP 0,Y . The EEPROM holds the absolute addresses of the routines in a table. In this way, a "pirate" could probably disassemble the main code in EPROM but he won't be able to know excatly what routine is really being called at the point of the JMP 0,X - sophisticated, isn't it ? :o) Kind regards, Roberto G. Berner 4308 3500 tel 4308 3700 fax 15 5122 6095 cel ----- Original Message ----- From: John Samperi To: Sent: Friday, December 06, 2002 7:59 PM Subject: RE: [m68HC11] Re: Security bit in HC711E9 - Thanks At 10:26 AM 6/12/02 -0600, you wrote: >> Still don't understand how issuing the command MS 103f 05 CLEARS the >> NOSEC bit (bit 3)when it is set in $05 (%00001001). Anyone from > >$05 is %00000101 Hmmmm I just go and get my long donkey's ears adjusted :-(( I guess that's the confused state one gets into by trying to decipher the docs that says that the HC711 CAN be secured (and there is an app note that explains how to do it) whilst in fact it cannot (thanks Darren). He ho he ho he ho... Regards John Samperi ****************************************************** Ampertronics Pty. Ltd. 11 Brokenwood Place Baulkham Hills, NSW 2153 AUSTRALIA Tel. (02) 9674-6495 Fax (02) 9674-8745 Email: Website http://ampertronics.com.au * Electronic Design * Technical Services * Contract Assembly ****************************************************** Yahoo! Groups Sponsor ADVERTISEMENT To unsubscribe from this group, send an email to: Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service. [Non-text portions of this message have been removed]

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