Development Support
Data Sheet
MC68HLC908QY/QT Family — Rev. 2
154
Development Support
MOTOROLA
15.2.3 Low-Power Modes
The WAIT and STOP instructions put the MCU in low power- consumption standby
modes. If enabled, the break module will remain enabled in wait and stop modes.
However, since the internal address bus does not increment in these modes, a
break interrupt will never be triggered.
15.3 Monitor Module (MON)
This subsection describes the monitor module (MON) and the monitor mode entry
methods. The monitor allows debugging and programming of the microcontroller
unit (MCU) through a single-wire interface with a host computer. Monitor mode
entry can be achieved without use of the higher test voltage, VTST, as long as
vector addresses $FFFE and $FFFF are blank, thus reducing the hardware
requirements for in-circuit programming.
Features include:
Normal user-mode pin functionality on most pins
One pin dedicated to serial communication between MCU and host
computer
Standard non-return-to-zero (NRZ) communication with host computer
Execution of code in random-access memory (RAM) or FLASH
FLASH memory security feature(1)
FLASH memory programming interface
Use of external 9.8304 MHz oscillator to generate internal frequency of
2.4576 MHz
Simple internal oscillator mode of operation (no external clock or high
voltage)
Monitor mode entry without high voltage, VTST, if reset vector is blank
($FFFE and $FFFF contain $FF)
Standard monitor mode entry if high voltage is applied to IRQ
15.3.1 Functional Description
Figure 15-10 shows a simplified diagram of monitor mode entry.
The monitor module receives and executes commands from a host computer.
enter monitor mode and communicate with a host computer via a standard RS-232
interface.
1. No security feature is absolutely secure. However, Motorola’s strategy is to make reading or
copying the FLASH difficult for unauthorized users.
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