AN2548 Freescale Semiconductor / Motorola, AN2548 Datasheet - Page 10

• Manufacturer Part Number: AN2548
• Description: Serial Monitor Program for HCS12 MCUs
• Manufacturer: Freescale Semiconductor / Motorola

AN2548/D
$B4 — Reset
10
B4 — When a user reset vector is programmed, the levels on the run/load
switch and the RxD0 line could cause a reset to either the user code or the
monitor. The sequence of checks to determine the type of reset is listed and
illustrated in
Warm start skips the long break output to SCI0. The warm reset is needed in
the case of an SCI0 Rx interrupt or SWI with an invalid SP value because the
interrupt stacking could have corrupted RAM or register values and because
the monitor cannot function without a valid stack.
Two pullup enable registers are modified during the monitor startup, but they
are restored to their reset values before going to the user reset location. The
INITRG, INITRM, INITEE registers are configured to promote compatibility as
described in EB386/D. The single write available to these registers is used so
that a single monitor program will support all HCS12 Family devices.
1. If the first byte of the user reset pseudo-vector = $FF
2. If the run/load switch = 0 (logic low), force monitor reset.
3. If RxD0 = 0 (logic low), force monitor reset.
4. If none of the above, use the reset pseudo-vector to jump to the
Freescale Semiconductor, Inc.
For More Information On This Product,
(unprogrammed), force monitor reset.
user reset start-up routine.
Serial Monitor Program for HCS12 MCUs
Figure
Go to: www.freescale.com
Figure 1. Determining Cause of Reset
1.
MONITOR RESET
0 (LOAD)
NO
YES
SWPORT = 0 OR 1
1 (RUN)
PROGRAMMED?
(LOAD OR RUN)?
USER RESET
USER CODE
YES
STARTUP
RxD0 = 0
NO
ENTER
?
MOTOROLA