Datasheet

MC68HC908QY4•MC68HC908QT4•MC68HC908QY2•MC68HC908QT2•MC68HC908QY1•MC68HC908QT1
120 Monitor ROM (MON) MOTOROLA
Monitor ROM (MON)
NON-DISCLOSURE AGREEMENT REQUIRED
The BIH and BIL instructions will behave as if the IRQ pin is enabled,
regardless of the settings in the configuration register. See Section 5.
Configuration Register (CONFIG).
The COP module is disabled in forced monitor mode. Any reset other
than a power-on reset (POR) will automatically force the MCU to come
back to the forced monitor mode.
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.
NOTE: Exiting monitor mode after it has been initiated by having a blank reset
vector requires a power-on reset (POR). Pulling RST (when RST pin
available) low will not exit monitor mode in this situation.
Table 9-2 summarizes the differences between user mode and monitor
mode regarding vectors.
9.4.2 V
TST
Monitor Mode
RST and OSC1 functions will be active on the PTA3 and PTA5 pins
respectively as long as V
TST
is applied to IRQ pin. If the IRQ pin is
lowered (no longer V
TST
) then the chip will still be operating in monitor
mode, but the pin functions will be determined by the settings in the
configuration registers (see Section 5. Configuration Register
(CONFIG)) when V
TST
was lowered, except for the IRQ pin. IRQ will not
function as a port input pin in monitor mode. Bit 2 of the Port A data
register will always read 0. The BIH and BIL instructions will behave as
if the IRQ pin is enabled, regardless of the settings in the configuration
registers.
Table 9-2. Mode Difference
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