| ??? 05/19/07 15:56 Read: times |
#139526 - hooks Responding to: ???'s previous message |
Erik,
I understand the need of mobile data download very well, being in a similar situation - the landline is often simply unavailable at a given site, fragile (easy to cut or intercept), or nowadays even prohibitively expensive when it comes to occasional data transmission, compared e.g. to GPRS/GSM, which is usually paid per byte transmitted, rather then per minute (plus a monthly fee) at the landline. Pathipati, I don't quite understand the need for 8x increase of data for encryption. Ther certainly is some increase because of packetised protocol overhead, but not so much. The standard block ciphers map the plain to encrypted data 1:1... Nevertheless, given the limited resources in microcontrollers, the standard way of accomplishing such small fixups is to insert "hooks" into the original program - arrange all function calls into a fixed-address jumptable, which in turn points to the real functions. Thus, if one of the functions has to be fixed, it is enough to rewrite the appropriate jump in the table to point to the new version of the function rather than the old one; and place this new function into the unused portion of FLASH. Simple, Stupid, but easy and working... JW |
| Topic | Author | Date |
| is DLL like modules possible with 8051 code ? | 01/01/70 00:00 | |
| Nothing new... | 01/01/70 00:00 | |
| If you choose the right part | 01/01/70 00:00 | |
| the code size is 128kb with banking ? | 01/01/70 00:00 | |
| is that this 'new math' I keep hearing about? | 01/01/70 00:00 | |
| How embarassing | 01/01/70 00:00 | |
| relative cost | 01/01/70 00:00 | |
| The real problem | 01/01/70 00:00 | |
| OP's position | 01/01/70 00:00 | |
| I'm guessing, too | 01/01/70 00:00 | |
| see my post | 01/01/70 00:00 | |
| security issues | 01/01/70 00:00 | |
| why not landline? that is waaay better | 01/01/70 00:00 | |
| it may be | 01/01/70 00:00 | |
| hooks | 01/01/70 00:00 | |
| with the right chip it can be done | 01/01/70 00:00 | |
| Details | 01/01/70 00:00 | |
| some, including me, agree . others .. | 01/01/70 00:00 | |
| I do it in a slightly different way | 01/01/70 00:00 | |
The "bios" version | 01/01/70 00:00 |