Datasheet

Functional Description
MC68HC908JL3E Family Data Sheet, Rev. 4
Freescale Semiconductor 75
Table 7-2 is a summary of the vector differences between user mode and monitor mode.
When the host computer has completed downloading code into the MCU RAM, the host then sends a
RUN command, which executes an RTI, which sends control to the address on the stack pointer.
7.3.2 Baud Rate
The communication baud rate is dependant on oscillator frequency. The state of PTB3 also affects baud
rate if entry to monitor mode is by IRQ
= V
TST
. When PTB3 is high, the divide by ratio is 1024. If the PTB3
pin is at logic zero upon entry into monitor mode, the divide by ratio is 512.
Table 7-2. Monitor Mode Vector Differences
Modes
Functions
COP
Reset
Vector
High
Reset
Vector
Low
Break
Vector
High
Break
Vector
Low
SWI
Vector
High
SWI
Vector
Low
User Enabled $FFFE $FFFF $FFFC $FFFD $FFFC $FFFD
Monitor
Disabled
(1)
$FEFE $FEFF $FEFC $FEFD $FEFC $FEFD
1. If the high voltage (V
TST
) is removed from the IRQ pin or the RST pin, the SIM asserts
its COP enable output. The COP is a mask option enabled or disabled by the COPD bit
in the configuration register.
Table 7-3. Monitor Baud Rate Selection
Monitor Mode
Entry By:
Input Clock
Frequency
PTB3 Baud Rate
IRQ
= V
TST
4.9152 MHz 0 9600 bps
9.8304 MHz 1 9600 bps
4.9152 MHz 1 4800 bps
Blank reset vector,
IRQ
= V
DD
9.8304 MHz X 9600 bps
4.9152 MHz X 4800 bps