mc908jl16 Freescale Semiconductor, Inc, mc908jl16 Datasheet - Page 184

• Manufacturer Part Number: mc908jl16
• Description: M68hc08 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

Development Support
16.3 Monitor Module (MON)
This section describes the monitor ROM (MON) and the monitor mode entry methods. The monitor ROM
allows complete testing of the MCU through a single-wire interface with a host computer. This mode is
also used for programming and erasing of FLASH memory in the MCU. Monitor mode entry can be
achieved without use of the higher test voltage, V
blank, thus reducing the hardware requirements for in-circuit programming.
Features include:
16.3.1 Functional Description
The monitor ROM receives and executes commands from a host computer.
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 most MCU pins retain normal operating mode functions. All
communication between the host computer and the MCU is through the PTB0 pin. A level-shifting and
multiplexing interface is required between PTB0 and the host computer. PTB0 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
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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
959 bytes monitor ROM code size
Monitor mode entry without high voltage, V
$FF)
Standard monitor mode entry if high voltage, V
Resident routines for FLASH programming and EEPROM emulation
MC68HC908JL16 Data Sheet, Rev. 1.1
(1)
TST
TST
, as long as vector addresses $FFFE and $FFFF are
, if reset vector is blank ($FFFE and $FFFF contain
TST
, is applied to IRQ
Figure 16-8
Freescale Semiconductor
shows a example