MC68HC908JB8 Datasheet, PDF (169/286 Pages) Motorola, Inc – MICROCONTROLLERS

Monitor ROM (MON)
Functional Description
Table 10-2 is a summary of the vector differences between user mode
and monitor mode.
Table 10-2. Monitor Mode Vector Differences
Functions
Modes
COP
Reset Reset Break Break SWI
SWI
Vector Vector Vector Vector Vector Vector
High Low High Low High Low
User
Enabled $FFFE $FFFF $FFFC $FFFD $FFFC $FFFD
Monitor _Disabled⁽¹⁾ $FEFE $FEFF $FEFC $FEFD $FEFC $FEFD
Notes:
1. If the high voltage (V_DD + V_HI) 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.
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.
10.4.2 Baud Rate
The communication baud rate is dependant on oscillator frequency,
f_XCLK. The state of PTA3 also affects baud rate if entry to monitor mode
is by IRQ = V_DD + V_HI. When PTA3 is high, the divide by ratio is 625. If
the PTA3 pin is at logic zero upon entry into monitor mode, the divide by
ratio is 312.
Table 10-3. Monitor Baud Rate Selection
Monitor Mode
Entry By:
IRQ = V_DD + V_HI
Blank reset vector,
IRQ = V_DD
Oscillator Clock
Frequency, f_CLK
3 MHz
6 MHz
3 MHz
6 MHz
3 MHz
PTA3
0
1
1
X
X
Baud Rate
9600 bps
9600 bps
4800 bps
9600 bps
4800 bps
MC68HC908JB8•MC68HC08JB8•MC68HC08JT8 — Rev. 2.3
Freescale Semiconductor
Monitor ROM (MON)
Technical Data
169