s908qc16vdse Freescale Semiconductor, Inc, s908qc16vdse Datasheet - Page 229

• Manufacturer Part Number: s908qc16vdse
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

If monitor mode was entered with V
IRQ.
18.3.1.2 Forced Monitor Mode
If entering monitor mode without high voltage on IRQ, then startup port pin requirements and conditions,
(PTA1/PTA4) are not in effect. This is to reduce circuit requirements when performing in-circuit
programming.
If monitor mode was entered as a result of the reset vector being blank, the COP is always disabled
regardless of the state of IRQ.
If the voltage applied to the IRQ is less than V
circuitry monitors the reset vector fetches and will assert an internal reset if it detects that the reset vectors
are erased ($FF). When the MCU comes out of reset, it is forced into monitor mode without requiring high
voltage on the IRQ pin. Once out of reset, the monitor code is initially executing with the internal clock at
its default frequency.
If IRQ is held high, all pins will default to regular input port functions except for PTA0 and PTA5 which will
operate as a serial communication port and OSC1 input respectively (refer to
allow the clock to be driven from an external source through OSC1 pin.
If IRQ is held low, all pins will default to regular input port function except for PTA0 which will operate as
serial communication port. Refer to
Regardless of the state of the IRQ pin, it 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 register. See
(CONFIG1 and
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.
18.3.1.3 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 18-2
Freescale Semiconductor
summarizes the differences between user mode and monitor mode regarding vectors.
If the reset vector is blank and monitor mode is entered, the chip will see an
additional reset cycle after the initial power-on reset (POR). Once the reset
vector has been programmed, the traditional method of applying a voltage,
V
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.
CONFIG2).
TST
MC68HC908QC16 • MC68HC908QC8 • MC68HC908QC4 Data Sheet, Rev. 4
, to IRQ must be used to enter monitor mode.
TST
Figure
on IRQ, then the COP is disabled as long as V
18-12.
TST
NOTE
NOTE
, the MCU will come out of reset in user mode. Internal
Chapter 4 Configuration Registers
Figure
Monitor Module (MON)
18-11). That will
TST
is applied to
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