Datasheet

Monitor ROM (MON)
Technical Data MC68HC908GR8 — Rev 4.0
194 Monitor ROM (MON) MOTOROLA
requirements and conditions, are not in effect. This is to reduce circuit
requirements when performing in-circuit programming.
NOTE: If the reset vector is blank and monitor mode is entered, the chip will see
an additional reset cycle after the initial POR reset. Once the part has
been programmed, the traditional method of applying a voltage, V
TST
, to
IRQ must be used to enter monitor mode.
The COP module is disabled in monitor mode based on these
conditions:
• If monitor mode was entered as a result of the reset vector being
blank (condition set 2 or 3), the COP is always disabled regardless
of the state of IRQ or RST.
• If monitor mode was entered with V
TST
on IRQ (condition set 1),
then the COP is disabled as long as V
TST
is applied to either IRQ
or RST.
The second 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.
Figure 15-2 shows a simplified diagram of the monitor mode entry when
the reset vector is blank and just 1 x V
DD
voltage is applied to the IRQ
pin. 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.
Frees
cale Semiconductor,
I
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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