
Monitor ROM (MON)
Technical Data
MC68HC08AZ32A — Rev 1.0
156
Monitor ROM (MON)
MOTOROLA
Execution of Code in RAM or ROM
EEPROM Programming
ROM Security (Read Protection)
(1)
EEPROM Read Protection
(1)
11.4 Functional description
The monitor ROM receives and executes commands from a host
computer.
Figure 11-1
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
MC68HC08AZ32A has optional ROM/EEPROM read protection
features to prevent external viewing of the contents of ROM/EEPROM
(see
Mask Options
on page 145). Proper procedures must be followed
to verify ROM/EEPROM content. Access to the ROM/EEPROM is
denied to unauthorized users of customer specified software with read
protection features enabled. See
Security
on page 164.
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 pull-up resistor.
1. No security feature is absolutely secure. However, Motorola’s strategy is to make reading or
copying the ROM/EEPROM data difficult for unauthorized users
F
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
n
.