3 break status register, 4 tbreak flag control register, 3 monitor rom (mon) – Freescale Semiconductor MC68HC908MR32 User Manual
Page 255: Break status register, Break flag control register, Monitor rom (mon)
Monitor ROM (MON)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
255
18.2.3.3 Break Status Register
The break status register (SBSR) contains a flag to indicate that a break caused an exit from wait mode.
The flag is useful in applications requiring a return to wait mode after exiting from a break interrupt.
BW — Break Wait Bit
This read/write bit is set when a break interrupt causes an exit from wait mode. Clear BW by writing a
logic 0 to it. Reset clears BW.
1 = Break interrupt during wait mode
0 = No break interrupt during wait mode
BW can be read within the break interrupt routine. The user can modify the return address on the stack
by subtracting 1 from it.
18.2.3.4 Break Flag Control Register
The break flag control register (SBFCR) contains a bit that enables software to clear status bits while the
MCU is in a break state.
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
18.3 Monitor ROM (MON)
The monitor ROM (MON) allows complete testing of the microcontroller unit (MCU) through a single-wire
interface with a host computer. Monitor mode entry can be achieved without the use of V
TST
as long as
vector addresses $FFFE and $FFFF are blank, thus reducing the hardware requirements for in-circuit
programming.
Address:
$FE00
Bit 7
6
5
4
3
2
1
Bit 0
Read:
R
R
R
R
R
R
BW
R
Write:
Reset:
0
Figure 18-6. SIM Break Status Register (SBSR)
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 18-7. SIM Break Flag Control Register (SBFCR)