MC68HC08AS32 Datasheet, PDF (160/394 Pages) Motorola, Inc – M68HC08 Family of 8-bit microcontroller units (MCUs)

Monitor ROM (MON)
12.3 Features
Features of the monitor ROM include:
• 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
12.4 Functional Description
Monitor ROM receives and executes commands from a host computer.
Figure 12-1 shows a sample circuit used to enter monitor mode and
communicate with a host computer via a standard RS-232 interface.
While simple monitor commands can access any memory address, the
MC68HC08AS32 has 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.
Advance Information
160
Monitor ROM (MON)
MC68HC08AS32 — Rev. 3.0
MOTOROLA