MC68HC708AS48 FREESCALE [Freescale Semiconductor, Inc], MC68HC708AS48 Datasheet - Page 162



Manufacturer Part Number
Advance Information
FREESCALE [Freescale Semiconductor, Inc]
Monitor ROM (MON)
12.3 Features
12.4 Functional Description
Advance Information
Features of the monitor ROM include:
Monitor ROM receives and executes commands from a host computer.
Figure 12-1
communicate with a host computer via a standard RS-232 interface.
While simple monitor commands can access any memory address, the
MC68HC708AS48 has an EPROM/OTPROM security feature that
requires proper procedures to be followed before the EPROM/OTPROM
can be accessed. Therefore, access to the EPROM/OTPROM 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 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 pullup resistor.
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–28.8 kbaud communication with host computer
Execution of code in RAM or EPROM/OTPROM
(E)EPROM/OTPROM programming
shows a sample circuit used to enter monitor mode and
Monitor ROM (MON)
Rev. 4.0

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