M68HC08 datasheet(116/288 Pages) FREESCALE

116 / 288 page

Monitor ROM (MON)

Data Sheet

MC68HC908BD48 — Rev. 2.1

116

Monitor ROM (MON)

Freescale Semiconductor

9.3 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

•

9600 Baud communication with host computer

•

Execution of code in RAM or FLASH

•

FLASH memory programming

9.4 Functional Description

The monitor ROM receives and executes commands from a host

computer. Figure 9-1 shows a sample 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 host-computer code in RAM while all MCU

pins 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 pull-up resistor.

M68HC08 Datasheet(PDF) 116 Page - Freescale Semiconductor, Inc