MC68HC08AS32A Datasheet, PDF (267/296 Pages) Motorola, Inc – Microcontrollers

Freescale Semiconductor, Inc.
Development Support
Monitor Module (MON)
17.2.3 Low-Power Modes
The WAIT and STOP instructions put the MCU in low-power standby modes. If
enabled, the break module will remain enabled in wait and stop modes. However,
since the internal address bus does not increment in these modes, a break
interrupt will never be triggered.
17.3 Monitor Module (MON)
This subsection describes the monitor module (MON) and the monitor mode entry
methods. The monitor allows debugging and programming of the microcontroller
unit (MCU) through a single-wire interface with a host computer.
Features include:
• Normal user-mode pin functionality on most pins
• One pin dedicated to serial communication between MCU and host
computer
• Standard non-return-to-zero (NRZ) communication with host computer
• 4800 Baud to 28.8 kBaud communication with host computer
• Execution of code in random-access memory (RAM) or FLASH
17.3.1 Functional Description
Figure 17-6 shows a simplified diagram of monitor mode entry.
The monitor module receives and executes commands from a host computer.
Figure 17-7 shows an example 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 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 pullup resistor.
17.3.1.1 Monitor Mode Entry
Table 17-1 shows the pin conditions for entering monitor mode. As specified in the
table, monitor mode may be entered after a power-on reset (POR) and will allow
communication provided the pin and clock conditions are met.
The rising edge of the internal RST signal latches the monitor mode. Once monitor
mode is latched, the values on PTC0, PTC1, and PTC3 pins can be changed.
Once out of reset, the MCU waits for the host to send eight security bytes
(see 17.3.2 Security). After the security bytes, the MCU sends a break signal
(10 consecutive logic 0s) to the host, indicating that it is ready to receive a
command.
MC68HC08AS32A — Rev. 1
MOTOROLA
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Data Sheet
267