SLAA685 Application note

SLAA685 December 2015 CC430F6125 , CC430F6125 , CC430F6126 , CC430F6126 , CC430F6127 , CC430F6127 , CC430F6135 , CC430F6135 , CC430F6137 , CC430F6137 , CC430F6147 , CC430F6147 , MSP430AFE221 , MSP430AFE221 , MSP430AFE222 , MSP430AFE222 , MSP430AFE223 , MSP430AFE223 , MSP430AFE231 , MSP430AFE231 , MSP430AFE232 , MSP430AFE232 , MSP430AFE233 , MSP430AFE233 , MSP430AFE251 , MSP430AFE251 , MSP430AFE252 , MSP430AFE252 , MSP430AFE253 , MSP430AFE253 , MSP430BT5190 , MSP430BT5190 , MSP430F1101 , MSP430F1101 , MSP430F1101A , MSP430F1101A , MSP430F1111A , MSP430F1111A , MSP430F112 , MSP430F112 , MSP430F1121 , MSP430F1121 , MSP430F1121A , MSP430F1121A , MSP430F1122 , MSP430F1122 , MSP430F1132 , MSP430F1132 , MSP430F122 , MSP430F122 , MSP430F1222 , MSP430F1222 , MSP430F123 , MSP430F123 , MSP430F1232 , MSP430F1232 , MSP430F133 , MSP430F133 , MSP430F135 , MSP430F135 , MSP430F147 , MSP430F147 , MSP430F1471 , MSP430F1471 , MSP430F148 , MSP430F148 , MSP430F1481 , MSP430F1481 , MSP430F149 , MSP430F149 , MSP430F1491 , MSP430F1491 , MSP430F155 , MSP430F155 , MSP430F156 , MSP430F156 , MSP430F157 , MSP430F157 , MSP430F1610 , MSP430F1610 , MSP430F1611 , MSP430F1611 , MSP430F1612 , MSP430F1612 , MSP430F167 , MSP430F167 , MSP430F168 , MSP430F168 , MSP430F169 , MSP430F169 , MSP430F2001 , MSP430F2001 , MSP430F2002 , MSP430F2002 , MSP430F2003 , MSP430F2003 , MSP430F2011 , MSP430F2011 , MSP430F2012 , MSP430F2012 , MSP430F2013 , MSP430F2013 , MSP430F2013-EP , MSP430F2013-EP , MSP430F2101 , MSP430F2101 , MSP430F2111 , MSP430F2111 , MSP430F2112 , MSP430F2112 , MSP430F2121 , MSP430F2121 , MSP430F2122 , MSP430F2122 , MSP430F2131 , MSP430F2131 , MSP430F2132 , MSP430F2132 , MSP430F2232 , MSP430F2232 , MSP430F2234 , MSP430F2234 , MSP430F2252 , MSP430F2252 , MSP430F2254 , MSP430F2254 , MSP430F2272 , MSP430F2272 , MSP430F2274 , MSP430F2274 , MSP430F233 , MSP430F233 , MSP430F2330 , MSP430F2330 , MSP430F235 , MSP430F235 , MSP430F2350 , MSP430F2350 , MSP430F2370 , MSP430F2370 , MSP430F2410 , MSP430F2410 , MSP430F2416 , MSP430F2416 , MSP430F2417 , MSP430F2417 , MSP430F2418 , MSP430F2418 , MSP430F2419 , MSP430F2419 , MSP430F247 , MSP430F247 , MSP430F2471 , MSP430F2471 , MSP430F248 , MSP430F248 , MSP430F2481 , MSP430F2481 , MSP430F249 , MSP430F249 , MSP430F2491 , MSP430F2491 , MSP430F2616 , MSP430F2616 , MSP430F2617 , MSP430F2617 , MSP430F2618 , MSP430F2618 , MSP430F2619 , MSP430F2619 , MSP430F412 , MSP430F412 , MSP430F413 , MSP430F413 , MSP430F4132 , MSP430F4132 , MSP430F415 , MSP430F415 , MSP430F4152 , MSP430F4152 , MSP430F417 , MSP430F417 , MSP430F423 , MSP430F423 , MSP430F423A , MSP430F423A , MSP430F425 , MSP430F425 , MSP430F4250 , MSP430F4250 , MSP430F425A , MSP430F425A , MSP430F4260 , MSP430F4260 , MSP430F427 , MSP430F427 , MSP430F4270 , MSP430F4270 , MSP430F427A , MSP430F427A , MSP430F435 , MSP430F435 , MSP430F4351 , MSP430F4351 , MSP430F436 , MSP430F436 , MSP430F4361 , MSP430F4361 , MSP430F437 , MSP430F437 , MSP430F4371 , MSP430F4371 , MSP430F438 , MSP430F438 , MSP430F439 , MSP430F439 , MSP430F447 , MSP430F447 , MSP430F448 , MSP430F448 , MSP430F4481 , MSP430F4481 , MSP430F449 , MSP430F449 , MSP430F4491 , MSP430F4491 , MSP430F4616 , MSP430F4616 , MSP430F46161 , MSP430F46161 , MSP430F4617 , MSP430F4617 , MSP430F46171 , MSP430F46171 , MSP430F4618 , MSP430F4618 , MSP430F46181 , MSP430F46181 , MSP430F4619 , MSP430F4619 , MSP430F46191 , MSP430F46191 , MSP430F47126 , MSP430F47126 , MSP430F47127 , MSP430F47127 , MSP430F47163 , MSP430F47163 , MSP430F47166 , MSP430F47166 , MSP430F47167 , MSP430F47167 , MSP430F47173 , MSP430F47173 , MSP430F47176 , MSP430F47176 , MSP430F47177 , MSP430F47177 , MSP430F47183 , MSP430F47183 , MSP430F47186 , MSP430F47186 , MSP430F47187 , MSP430F47187 , MSP430F47193 , MSP430F47193 , MSP430F47196 , MSP430F47196 , MSP430F47197 , MSP430F47197 , MSP430F477 , MSP430F477 , MSP430F478 , MSP430F478 , MSP430F4783 , MSP430F4783 , MSP430F4784 , MSP430F4784 , MSP430F479 , MSP430F479 , MSP430F4793 , MSP430F4793 , MSP430F4794 , MSP430F4794 , MSP430F5212 , MSP430F5212 , MSP430F5214 , MSP430F5214 , MSP430F5217 , MSP430F5217 , MSP430F5219 , MSP430F5219 , MSP430F5222 , MSP430F5222 , MSP430F5224 , MSP430F5224 , MSP430F5229 , MSP430F5229 , MSP430F5232 , MSP430F5232 , MSP430F5234 , MSP430F5234 , MSP430F5237 , MSP430F5237 , MSP430F5239 , MSP430F5239 , MSP430F5242 , MSP430F5242 , MSP430F5244 , MSP430F5244 , MSP430F5247 , MSP430F5247 , MSP430F5249 , MSP430F5249 , MSP430F5252 , MSP430F5252 , MSP430F5253 , MSP430F5253 , MSP430F5254 , MSP430F5254 , MSP430F5255 , MSP430F5255 , MSP430F5256 , MSP430F5256 , MSP430F5257 , MSP430F5257 , MSP430F5258 , MSP430F5258 , MSP430F5259 , MSP430F5259 , MSP430F5304 , MSP430F5304 , MSP430F5308 , MSP430F5308 , MSP430F5309 , MSP430F5309 , MSP430F5310 , MSP430F5310 , MSP430F5324 , MSP430F5324 , MSP430F5325 , MSP430F5325 , MSP430F5326 , MSP430F5326 , MSP430F5327 , MSP430F5327 , MSP430F5328 , MSP430F5328 , MSP430F5329 , MSP430F5329 , MSP430F5333 , MSP430F5333 , MSP430F5335 , MSP430F5335 , MSP430F5336 , MSP430F5336 , MSP430F5338 , MSP430F5338 , MSP430F5340 , MSP430F5340 , MSP430F5341 , MSP430F5341 , MSP430F5342 , MSP430F5342 , MSP430F5358 , MSP430F5358 , MSP430F5359 , MSP430F5359 , MSP430F5418 , MSP430F5418 , MSP430F5418A , MSP430F5418A , MSP430F5419 , MSP430F5419 , MSP430F5419A , MSP430F5419A , MSP430F5435 , MSP430F5435 , MSP430F5435A , MSP430F5435A , MSP430F5436 , MSP430F5436 , MSP430F5436A , MSP430F5436A , MSP430F5437 , MSP430F5437 , MSP430F5437A , MSP430F5437A , MSP430F5438 , MSP430F5438 , MSP430F5438A , MSP430F5438A , MSP430F5500 , MSP430F5500 , MSP430F5501 , MSP430F5501 , MSP430F5502 , MSP430F5502 , MSP430F5503 , MSP430F5503 , MSP430F5504 , MSP430F5504 , MSP430F5505 , MSP430F5505 , MSP430F5506 , MSP430F5506 , MSP430F5507 , MSP430F5507 , MSP430F5508 , MSP430F5508 , MSP430F5509 , MSP430F5509 , MSP430F5510 , MSP430F5510 , MSP430F5513 , MSP430F5513 , MSP430F5514 , MSP430F5514 , MSP430F5515 , MSP430F5515 , MSP430F5517 , MSP430F5517 , MSP430F5519 , MSP430F5519 , MSP430F5521 , MSP430F5521 , MSP430F5522 , MSP430F5522 , MSP430F5524 , MSP430F5524 , MSP430F5525 , MSP430F5525 , MSP430F5526 , MSP430F5526 , MSP430F5527 , MSP430F5527 , MSP430F5528 , MSP430F5528 , MSP430F5529 , MSP430F5529 , MSP430F5630 , MSP430F5630 , MSP430F5631 , MSP430F5631 , MSP430F5632 , MSP430F5632 , MSP430F5633 , MSP430F5633 , MSP430F5634 , MSP430F5634 , MSP430F5635 , MSP430F5635 , MSP430F5636 , MSP430F5636 , MSP430F5637 , MSP430F5637 , MSP430F5638 , MSP430F5638 , MSP430F5658 , MSP430F5658 , MSP430F5659 , MSP430F5659 , MSP430F6433 , MSP430F6433 , MSP430F6435 , MSP430F6435 , MSP430F6436 , MSP430F6436 , MSP430F6438 , MSP430F6438 , MSP430F6458 , MSP430F6458 , MSP430F6459 , MSP430F6459 , MSP430F6630 , MSP430F6630 , MSP430F6631 , MSP430F6631 , MSP430F6632 , MSP430F6632 , MSP430F6633 , MSP430F6633 , MSP430F6634 , MSP430F6634 , MSP430F6635 , MSP430F6635 , MSP430F6636 , MSP430F6636 , MSP430F6637 , MSP430F6637 , MSP430F6638 , MSP430F6638 , MSP430F6658 , MSP430F6658 , MSP430F6659 , MSP430F6659 , MSP430F6745 , MSP430F6745 , MSP430F67451 , MSP430F67451 , MSP430F67451A , MSP430F67451A , MSP430F6745A , MSP430F6745A , MSP430F6746 , MSP430F6746 , MSP430F67461 , MSP430F67461 , MSP430F67461A , MSP430F67461A , MSP430F6746A , MSP430F6746A , MSP430F6747 , MSP430F6747 , MSP430F67471 , MSP430F67471 , MSP430F67471A , MSP430F67471A , MSP430F6747A , MSP430F6747A , MSP430F6748 , MSP430F6748 , MSP430F67481 , MSP430F67481 , MSP430F67481A , MSP430F67481A , MSP430F6748A , MSP430F6748A , MSP430F6749 , MSP430F6749 , MSP430F67491 , MSP430F67491 , MSP430F67491A , MSP430F67491A , MSP430F6749A , MSP430F6749A , MSP430F67621 , MSP430F67621 , MSP430F67621A , MSP430F67621A , MSP430F67641 , MSP430F67641 , MSP430F67641A , MSP430F67641A , MSP430F6765 , MSP430F6765 , MSP430F67651 , MSP430F67651 , MSP430F67651A , MSP430F67651A , MSP430F6765A , MSP430F6765A , MSP430F6766 , MSP430F6766 , MSP430F67661 , MSP430F67661 , MSP430F67661A , MSP430F67661A , MSP430F6766A , MSP430F6766A , MSP430F6767 , MSP430F6767 , MSP430F67671 , MSP430F67671 , MSP430F67671A , MSP430F67671A , MSP430F6767A , MSP430F6767A , MSP430F6768 , MSP430F6768 , MSP430F67681 , MSP430F67681 , MSP430F67681A , MSP430F67681A , MSP430F6768A , MSP430F6768A , MSP430F6769 , MSP430F6769 , MSP430F67691 , MSP430F67691 , MSP430F67691A , MSP430F67691A , MSP430F6769A , MSP430F6769A , MSP430F6775 , MSP430F6775 , MSP430F67751 , MSP430F67751 , MSP430F67751A , MSP430F67751A , MSP430F6775A , MSP430F6775A , MSP430F6776 , MSP430F6776 , MSP430F67761 , MSP430F67761 , MSP430F67761A , MSP430F67761A , MSP430F6776A , MSP430F6776A , MSP430F6777 , MSP430F6777 , MSP430F67771 , MSP430F67771 , MSP430F67771A , MSP430F67771A , MSP430F6777A , MSP430F6777A , MSP430F6778 , MSP430F6778 , MSP430F67781 , MSP430F67781 , MSP430F67781A , MSP430F67781A , MSP430F6778A , MSP430F6778A , MSP430F6779 , MSP430F6779 , MSP430F67791 , MSP430F67791 , MSP430F67791A , MSP430F67791A , MSP430F6779A , MSP430F6779A , MSP430FE423 , MSP430FE423 , MSP430FE4232 , MSP430FE4232 , MSP430FE423A , MSP430FE423A , MSP430FE4242 , MSP430FE4242 , MSP430FE425 , MSP430FE425 , MSP430FE4252 , MSP430FE4252 , MSP430FE425A , MSP430FE425A , MSP430FE427 , MSP430FE427 , MSP430FE4272 , MSP430FE4272 , MSP430FE427A , MSP430FE427A , MSP430FG4250 , MSP430FG4250 , MSP430FG4260 , MSP430FG4260 , MSP430FG4270 , MSP430FG4270 , MSP430FG437 , MSP430FG437 , MSP430FG438 , MSP430FG438 , MSP430FG439 , MSP430FG439 , MSP430FG4616 , MSP430FG4616 , MSP430FG4617 , MSP430FG4617 , MSP430FG4618 , MSP430FG4618 , MSP430FG4619 , MSP430FG4619 , MSP430FG477 , MSP430FG477 , MSP430FG478 , MSP430FG478 , MSP430FG479 , MSP430FG479 , MSP430FR2032 , MSP430FR2032 , MSP430FR2033 , MSP430FR2033 , MSP430FR2110 , MSP430FR2110 , MSP430FR2111 , MSP430FR2111 , MSP430FR2311 , MSP430FR2311 , MSP430FR2433 , MSP430FR2433 , MSP430FR2532 , MSP430FR2532 , MSP430FR2533 , MSP430FR2533 , MSP430FR2632 , MSP430FR2632 , MSP430FR2633 , MSP430FR2633 , MSP430FR4131 , MSP430FR4131 , MSP430FR4132 , MSP430FR4132 , MSP430FR5720 , MSP430FR5720 , MSP430FR5721 , MSP430FR5721 , MSP430FR5722 , MSP430FR5722 , MSP430FR5723 , MSP430FR5723 , MSP430FR5724 , MSP430FR5724 , MSP430FR5725 , MSP430FR5725 , MSP430FR5726 , MSP430FR5726 , MSP430FR5727 , MSP430FR5727 , MSP430FR5728 , MSP430FR5728 , MSP430FR5729 , MSP430FR5729 , MSP430FR5730 , MSP430FR5730 , MSP430FR5731 , MSP430FR5731 , MSP430FR5732 , MSP430FR5732 , MSP430FR5733 , MSP430FR5733 , MSP430FR5734 , MSP430FR5734 , MSP430FR5735 , MSP430FR5735 , MSP430FR5736 , MSP430FR5736 , MSP430FR5737 , MSP430FR5737 , MSP430FR5738 , MSP430FR5738 , MSP430FR5739 , MSP430FR5739 , MSP430FR5847 , MSP430FR5847 , MSP430FR58471 , MSP430FR58471 , MSP430FR5848 , MSP430FR5848 , MSP430FR5849 , MSP430FR5849 , MSP430FR5857 , MSP430FR5857 , MSP430FR5858 , MSP430FR5858 , MSP430FR5859 , MSP430FR5859 , MSP430FR5867 , MSP430FR5867 , MSP430FR58671 , MSP430FR58671 , MSP430FR5868 , MSP430FR5868 , MSP430FR5869 , MSP430FR5869 , MSP430FR5870 , MSP430FR5870 , MSP430FR5872 , MSP430FR5872 , MSP430FR58721 , MSP430FR58721 , MSP430FR5887 , MSP430FR5887 , MSP430FR5888 , MSP430FR5888 , MSP430FR5889 , MSP430FR5889 , MSP430FR58891 , MSP430FR58891 , MSP430FR5922 , MSP430FR5922 , MSP430FR59221 , MSP430FR59221 , MSP430FR5947 , MSP430FR5947 , MSP430FR59471 , MSP430FR59471 , MSP430FR5948 , MSP430FR5948 , MSP430FR5949 , MSP430FR5949 , MSP430FR5957 , MSP430FR5957 , MSP430FR5958 , MSP430FR5958 , MSP430FR5959 , MSP430FR5959 , MSP430FR5967 , MSP430FR5967 , MSP430FR5968 , MSP430FR5968 , MSP430FR5969 , MSP430FR5969 , MSP430FR5969-SP , MSP430FR5969-SP , MSP430FR59691 , MSP430FR59691 , MSP430FR5970 , MSP430FR5970 , MSP430FR5972 , MSP430FR5972 , MSP430FR59721 , MSP430FR59721 , MSP430FR5986 , MSP430FR5986 , MSP430FR5987 , MSP430FR5987 , MSP430FR5988 , MSP430FR5988 , MSP430FR5989 , MSP430FR5989 , MSP430FR5989-EP , MSP430FR5989-EP , MSP430FR59891 , MSP430FR59891 , MSP430FR5994 , MSP430FR5994 , MSP430FR6820 , MSP430FR6820 , MSP430FR6822 , MSP430FR6822 , MSP430FR68221 , MSP430FR68221 , MSP430FR6870 , MSP430FR6870 , MSP430FR6872 , MSP430FR6872 , MSP430FR68721 , MSP430FR68721 , MSP430FR6877 , MSP430FR6877 , MSP430FR6879 , MSP430FR6879 , MSP430FR68791 , MSP430FR68791 , MSP430FR6887 , MSP430FR6887 , MSP430FR6888 , MSP430FR6888 , MSP430FR6889 , MSP430FR6889 , MSP430FR68891 , MSP430FR68891 , MSP430FR6920 , MSP430FR6920 , MSP430FR6922 , MSP430FR6922 , MSP430FR69221 , MSP430FR69221 , MSP430FR6927 , MSP430FR6927 , MSP430FR69271 , MSP430FR69271 , MSP430FR6928 , MSP430FR6928 , MSP430FR6970 , MSP430FR6970 , MSP430FR6972 , MSP430FR6972 , MSP430FR69721 , MSP430FR69721 , MSP430FR6977 , MSP430FR6977 , MSP430FR6979 , MSP430FR6979 , MSP430FR69791 , MSP430FR69791 , MSP430FR6987 , MSP430FR6987 , MSP430FR6988 , MSP430FR6988 , MSP430FR6989 , MSP430FR6989 , MSP430FR69891 , MSP430FR69891 , MSP430FW423 , MSP430FW423 , MSP430FW425 , MSP430FW425 , MSP430FW427 , MSP430FW427 , MSP430FW428 , MSP430FW428 , MSP430FW429 , MSP430FW429 , MSP430G2001 , MSP430G2001 , MSP430G2101 , MSP430G2101 , MSP430G2102 , MSP430G2102 , MSP430G2111 , MSP430G2111 , MSP430G2112 , MSP430G2112 , MSP430G2121 , MSP430G2121 , MSP430G2131 , MSP430G2131 , MSP430G2132 , MSP430G2132 , MSP430G2152 , MSP430G2152 , MSP430G2153 , MSP430G2153 , MSP430G2201 , MSP430G2201 , MSP430G2202 , MSP430G2202 , MSP430G2203 , MSP430G2203 , MSP430G2210 , MSP430G2210 , MSP430G2211 , MSP430G2211 , MSP430G2212 , MSP430G2212 , MSP430G2213 , MSP430G2213 , MSP430G2221 , MSP430G2221 , MSP430G2230 , MSP430G2230 , MSP430G2231 , MSP430G2231 , MSP430G2232 , MSP430G2232 , MSP430G2233 , MSP430G2233 , MSP430G2252 , MSP430G2252 , MSP430G2253 , MSP430G2253 , MSP430G2302 , MSP430G2302 , MSP430G2303 , MSP430G2303 , MSP430G2312 , MSP430G2312 , MSP430G2313 , MSP430G2313 , MSP430G2332 , MSP430G2332 , MSP430G2333 , MSP430G2333 , MSP430G2352 , MSP430G2352 , MSP430G2353 , MSP430G2353 , MSP430G2402 , MSP430G2402 , MSP430G2403 , MSP430G2403 , MSP430G2412 , MSP430G2412 , MSP430G2413 , MSP430G2413 , MSP430G2432 , MSP430G2432 , MSP430G2433 , MSP430G2433 , MSP430G2444 , MSP430G2444 , MSP430G2452 , MSP430G2452 , MSP430G2453 , MSP430G2453 , MSP430G2513 , MSP430G2513 , MSP430G2533 , MSP430G2533 , MSP430G2544 , MSP430G2544 , MSP430G2553 , MSP430G2553 , MSP430G2744 , MSP430G2744 , MSP430G2755 , MSP430G2755 , MSP430G2855 , MSP430G2855 , MSP430G2955 , MSP430G2955 , MSP430L092 , MSP430L092 , MSP430TCH5E , MSP430TCH5E , MSP430V294 , MSP430V294

MSP Code Protection Features

4.1 Password Protection

All MSP430 bootloaders provide password protection on some commands. Typically, any commands that allow readout of the device, like TX_DATA_BLOCK, or control of the device, like Load PC or RX_DATA_BLOCK, are protected and do not execute unless the correct password was already provided. Usually, the only commands not protected are RX_PASSWORD to receive the BSL password and unlock the other commands, CHANGE_BAUD_RATE for changing the BSL baud rate to facilitate BSL communication, and MASS_ERASE for totally wiping the device memory.

The password consists of a number of bytes, typically 32 bytes, located at the end of the interrupt vector table up to memory address 0xFFFF (see the BSL user's guide for more details on specific addresses for the device). Almost all MSP430 BSLs have the password being made up of the data at the addresses 0xFFE0-0xFFFF (excluding only MSP430F54xx non-A devices that have only a 16-byte password).

Because the BSL password consists of values from the device interrupt vector table (IVT), on a programmed device the IVT always has a value other than 0xFFFF at least for the reset vector at address 0xFFFE (in addition to any other interrupt vectors used in the application), there is always some BSL password set simply by loading a program into the device.

In CCS, if any interrupt vectors have no ISRs defined by the user, the TI C/C++ compiler automatically adds a trap ISR to catch any of these unused vectors. Because of this, the unused vectors have some value other than 0xFFFF, but it is the same value for all unused vectors. This adds some more values to the password, but if the user code is not using many interrupts it still might not have very much variation to it.

@FFE0
1A 4C 1A 4C 1A 4C 1A 4C 1A 4C 9C 48 1A 4C 1A 4C
1A 4C 1A 4C 1A 4C 1A 4C 1A 4C 1A 4C 1A 4C 00 4C

In the TI-txt file snippet above, observe the IVT area that contains the BSL password – 32 bytes between 0xFFE0-0xFFFF. The values 489Ch and 4C00h are highlighted in green text (these are used interrupt vectors) in this example, for one of the Timer ISRs and for the Reset vector. Observe how the reset vector at FFFEh is indicating that the start-up code begins at 4C00h. All other IVT entries, which are unused, have been filled with 4C1Ah – this is the address of the trap ISR. Looking in the .map file, the address of the trap ISR is also found, marked __TI_ISR_TRAP. Other ISR addresses are also found under the _isr section.

.text:_isr
*          0    00004c00    00000020
                  00004c00    0000001a     rts430x_lc_rd_eabi.lib : boot_special.obj (.text:_isr:_c_int00_noargs_noexit)
                  00004c1a    00000006                            : isr_trap.obj (.text:_isr:__TI_ISR_TRAP)

If it is desired to customize the BSL password, the unused entries of the IVT could be modified to other values for the password. However, the danger in this case is that if an interrupt comes in, the IVT entry is used as the address for code execution to jump to, so putting random values here could cause code to run wild or reset the part especially if an erroneous interrupt occurs (for example if an interrupt had been enabled unintentionally). This may not be a very likely scenario but still does pose some risk, and therefore, the user must decide based on their system and application. Alternately, the user can define separate ISRs for all unused interrupts with IVT entries in the BSL password area FFE0h–FFFFh, and use linker file modification and pragmas to place these at desired addresses to create the desired BSL password.