Datasheet

Monitor ROM (MON)
Technical Data MC68HC908GR8 — Rev 4.0
196 Monitor ROM (MON) MOTOROLA
Table 15-2 summarizes the differences between user mode and monitor
mode.
15.4.2 Data Format
Communication with the monitor ROM is in standard non-return-to-zero
(NRZ) mark/space data format. Transmit and receive baud rates must
be identical.
Figure 15-3. Monitor Data Format
15.4.3 Break Signal
A start bit (logic 0) followed by nine logic 0 bits is a break signal. When
the monitor receives a break signal, it drives the PTA0 pin high for the
duration of two bits and then echoes back the break signal.
Figure 15-4. Break Transaction
Table 15-2. Mode Differences
Modes
Functions
Reset
Vector
High
Reset
Vector
Low
Break
Vector
High
Break
Vector
Low
SWI
Vector
High
SWI
Vector
Low
User $FFFE $FFFF $FFFC $FFFD $FFFC $FFFD
Monitor $FEFE $FEFF $FEFC $FEFD $FEFC $FEFD
BIT 5
START
BIT
BIT 1
NEXT
STOP
BIT
START
BIT
BIT 2 BIT 3 BIT 4 BIT 7BIT 0
BIT 6
0 1 2 3 4 5 6 7
0 1 2 3 4 5 6 7
MISSING STOP BIT
2-STOP BIT DELAY BEFORE ZERO ECHO
Frees
cale Semiconductor,
I
Freescale Semiconductor, Inc.
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