mc68hc08ln56 Freescale Semiconductor, Inc, mc68hc08ln56 Datasheet - Page 223

• Manufacturer Part Number: mc68hc08ln56
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Chapter 21
Monitor ROM (MON)
21.1 Introduction
This section describes the use of the monitor ROM (MON08) firmware. Execution of code in the monitor
ROM in monitor mode allows complete testing of the MCU through a single-wire interface with a host
computer.
21.2 Features
Features of monitor mode include the following:
21.3 Functional Description
The monitor ROM receives and executes commands from a host computer.
example circuit used to enter monitor mode and communicate with a host computer via a standard
RS-232 interface.
Simple monitor commands can access any memory address. In monitor mode, the MCU can execute
code in RAM which has been loaded by the host computer, while all MCU pins retain normal operating
mode functions. All communication between the host computer and the MCU is through the PTA0 pin, at
a chosen baud rate. 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.
Freescale Semiconductor
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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
Execution of Code in either RAM or ROM/EPROM
(E)EPROM/OTPROM Programming
MC68HC08LN56 • MC68HC708LN56 General Release Specification, Rev. 2.1
Figure 21-1
shows an
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