Siemens 88C166 16-bit microcontrollers provide 32 KBytes Flash memory on-chip, which can be protected against data operand acceses and program branches into the Flash from any location outside the Flash. This Application Note gives hints and examples how the Flash protection on 88C166 Flash devices can be enabled and how the protection can be temporary disabled (e.g. for program updates) by a program running inside the Flash. Author : Peter Kliegelhöfer / HL DC AT Microcontroller Application Support 1 Introduction . . . . . 3 2 Flash Protection . 3 3 Test Mode Selection . . 4 4 Test Environment 6 5 Miscellaneous . . . 8 5.1 Bootstrap Loader Activation . 8 5.2 NMI Circuit . . . . . 9 5.3 Delay Logic . . . . 10 5.4 Testing . . . . . . . 11 6 Appendix . . . . . . 12 A PROT166.A66 12ff B UNLOCK.A66 . . 15 C C166_F.EQU . . . 16 D PROT166_.EQU 16 E UNLOCK_.EQU 16f F PROT166.ILO . . 17 G PROT166.BAT . 17 H UFP166.A66 . . .18f I UFP166.ILO . . . 19 J UFP166.BAT . . . 20