MC68HC08JK1 Datasheet, PDF (96/198 Pages) Motorola, Inc – HCMOS Microcontroller Unit

Freescale Semiconductor, Inc.
Monitor ROM (MON)
9.3 Features
Features of the monitor ROM include the following:
• 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 to 28.8 k-Baud communication with host computer
• Execution of code in RAM or ROM
9.4 Functional Description
The monitor ROM receives and executes commands from a host
computer. Figure 9-1 shows a example 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
MCU 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 PTB0 retain normal operating mode functions.
All communication between the host computer and the MCU is through
the PTB0 pin. A level-shifting and multiplexing interface is required
between PTB0 and the host computer. PTB0 is used in a wired-OR
configuration and requires a pull-up resistor.
Technical Data
96
Monitor ROM (MON)
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MC68H(R)C08JL3 — Rev. 4
MOTOROLA