MC68HC08GP32A Datasheet, PDF (223/258 Pages) Freescale Semiconductor, Inc – Microcontrollers

Monitor Module (MON)
19.2.2.4 Break Flag Control Register
The break control register (SBFCR) contains a bit that enables software to clear status bits while the MCU
is in a break state.
Address: $FE03
Bit 7
6
5
4
3
2
1
Bit 0
Read:
BCFE
R
R
R
R
R
R
R
Write:
Reset: 0
R = Reserved
Figure 19-7. Break Flag Control Register (SBFCR)
BCFE — Break Clear Flag Enable Bit
This read/write bit enables software to clear status bits by accessing status registers while the MCU is
in a break state. To clear status bits during the break state, the BCFE bit must be set.
1 = Status bits clearable during break
0 = Status bits not clearable during break
19.2.3 Low-Power Modes
The WAIT and STOP instructions put the MCU in low power-consumption 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.
19.3 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
• 9600 Baud communication with host computer
• Execution of code in random-access memory (RAM) or ROM
19.3.1 Functional Description
Figure 19-8 shows a simplified diagram of monitor mode entry.
The monitor module receives and executes commands from a host computer.
Figure 19-9 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.
MC68HC08GP32A • MC68HC08GP16A Data Sheet, Rev. 1.0
Freescale Semiconductor
223