Advance Information MC68HC(7)08KH12Rev. 1.1
150 Freescale Semiconductor
10.3 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 kBaud Communication with Host Computer
Execution of Code in RAM or ROM
OTPROM Programming
10.4 Functional Description
The monitor ROM receives and executes commands from a host
computer. Figure 10-1 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.