mc68hc908ld64 Freescale Semiconductor, Inc, mc68hc908ld64 Datasheet - Page 138

• Manufacturer Part Number: mc68hc908ld64
• Description: M68hc08 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

Monitor ROM (MON)
10.3 Features
10.4 Functional Description
Data Sheet
138
Features of the monitor ROM include:
The monitor ROM receives and executes commands from a host
computer.
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 downloaded into RAM by a host
computer while most 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.
1. No security feature is absolutely secure. However, Freescale’s strategy is to make reading or
copying the FLASH difficult for unauthorized users.
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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 RAM or FLASH
FLASH memory security feature
FLASH memory programming interface
1024 bytes monitor ROM code size ($FA00 to $FDFF)
Monitor mode entry without high voltage, V
blank ($FFFE and $FFFF contain $FF)
Standard monitor mode entry if high voltage, V
IRQ
Figure 10-1
Monitor ROM (MON)
shows a sample circuit used to enter monitor
1
MC68HC908LD64
TST
Freescale Semiconductor
, if reset vector is
TST
, is applied to
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Rev. 3.0