MC68HC08LT8 Datasheet, PDF (142/156 Pages) Freescale Semiconductor, Inc – Microcontrollers

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15.3 Monitor Module (MON)
The monitor module allows complete testing of the microcontroller unit (MCU) through a single-wire
interface with a host computer. Monitor mode entry can be achieved without use of the higher test voltage,
V_TST, as long as vector addresses $FFFE and $FFFF are blank, thus reducing the hardware
requirements for in-circuit programming.
Features of the monitor module include:
• Normal user-mode pin functionality
• One pin dedicated to serial communication between MCU and host computer
• Standard non-return-to-zero (NRZ) communication with host computer
• Standard communication baud rate (9600 @ 2.4576-MHz internal operating frequency)
• Execution of code in random-access memory (RAM) or ROM
• ROM security feature⁽¹⁾
• Use of external 4.9152MHz or 9.8304MHz oscillator to generate internal operating frequency of
2.4576 MHz
• Normal monitor mode entry if V_TST is applied to IRQ
1. No security feature is absolutely secure. However, Freescale’s strategy is to make reading or copying the ROM difficult for
unauthorized users.
MC68HC08LT8 Data Sheet, Rev. 1
142
Freescale Semiconductor