MC68HC908GR16 Datasheet, PDF (274/310 Pages) Motorola, Inc – Microcontrollers

Freescale Semiconductor, Inc.
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This condition states that as long as V_TST is maintained on the IRQ pin after
entering monitor mode, or if V_TST is applied to RST after the initial reset to get into
monitor mode (when V_TST was applied to IRQ), then the COP will be disabled. In
the latter situation, after V_TST is applied to the RST pin, V_TST can be removed from
the IRQ pin in the interest of freeing the IRQ for normal functionality in monitor
mode.
19.3.1.2 Forced Monitor Mode
If entering monitor mode without high voltage on IRQ, then all port B pin
requirements and conditions, including the PTB4 frequency divisor selection, are
not in effect. This is to reduce circuit requirements when performing in-circuit
programming.
NOTE:
Once the reset vector has been programmed, the traditional method of applying a
voltage, V_TST, to IRQ must be used to enter monitor mode.
An external oscillator of 9.8304 MHz is required for a baud rate of 9600, as the
internal bus frequency is automatically set to the external frequency divided by
four.
When the forced monitor mode is entered the COP is always disabled regardless
of the state of IRQ or RST.
19.3.1.3 Monitor Vectors
In monitor mode, the MCU uses different vectors for reset, SWI (software interrupt),
and break interrupt than those for user mode. The alternate vectors are in the $FE
page instead of the $FF page and allow code execution from the internal monitor
firmware instead of user code.
Table 19-2 summarizes the differences between user mode and monitor mode.
Table 19-2. Mode Differences
Modes
Reset
Vector High
Reset
Vector Low
Functions
Break
Break
Vector High Vector Low
SWI
Vector High
SWI
Vector Low
User
$FFFE
$FFFF
$FFFC
$FFFD
$FFFC
$FFFD
Monitor $FEFE
$FEFF
$FEFC
$FEFD
$FEFC
$FEFD
Data Sheet
274
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MC68HC908GR16 — Rev. 1.0
MOTOROLA