M68HC11 Datasheet, PDF (277/336 Pages) Motorola, Inc – Technical Data

Motorola Semiconductor Application Note
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by AN1060/D
Rev. 1.0
AN1060
M68HC11 Bootstrap Mode
By Jim Sibigtroth, Mike Rhoades, and John Langan
Austin, Texas
Introduction
The M68HC11 Family of MCUs (microcontroller units) has a bootstrap
mode that allows a user-defined program to be loaded into the internal
random-access memory (RAM) by way of the serial communications
interface (SCI); the M68HC11 then executes this loaded program. The
loaded program can do anything a normal user program can do as well
as anything a factory test program can do because protected control bits
are accessible in bootstrap mode. Although the bootstrap mode is a
single-chip mode of operation, expanded mode resources are
accessible because the mode control bits can be changed while
operating in the bootstrap mode.
This application note explains the operation and application of the
M68HC11 bootstrap mode. Although basic concepts associated with this
mode are quite simple, the more subtle implications of these functions
require careful consideration. Useful applications of this mode are
overlooked due to an incomplete understanding of bootstrap mode.
Also, common problems associated with bootstrap mode could be
avoided by a more complete understanding of its operation and
implications.
© Motorola, Inc., 1999
AN1060 — Rev. 1.0