mc68hc08qa24 Freescale Semiconductor, Inc, mc68hc08qa24 Datasheet - Page 166

• Manufacturer Part Number: mc68hc08qa24
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Monitor ROM (MON)
13.3 Features
13.4 Functional Description
Technical Data
164
Features of the monitor ROM include:
Monitor ROM receives and executes commands from a host computer.
Figure 13-1
communicate with a host computer via a standard RS-232 interface.
While simple monitor commands can access any memory address, the
MC68HC08QA24has a ROM security feature that requires proper
procedures to be followed before the ROM can be accessed. Access to
the ROM is denied to unauthorized users of customer-specified
software.
In monitor mode, the MCU can execute host-computer code in RAM
while all MCU pins except PTA0 retain normal operating mode functions.
All communication between the host computer and the MCU is through
the PTA0 pin. A level-shifting and multiplexing interface is required
between PTA0 and the host computer. PTA0 is used in a wired-OR
configuration and requires a pullup resistor.
•
•
•
•
•
Normal user-mode pin functionality
One pin dedicated to serial communication between monitor ROM
and host computer
Standard mark/space non-return-to-zero (NRZ) communication
with host computer
4800 baud–28.8 Kbaud communication with host computer
Execution of code in RAM or ROM
shows a sample circuit used to enter monitor mode and
Monitor ROM (MON)
Freescale Semiconductor
MC68HC08QA24