m37905 Renesas Electronics Corporation., m37905 Datasheet - Page 396

• Manufacturer Part Number: m37905
• Description: Mitsubishi 16-bit Single-chip Microcomputer 7700 Family / 7900 Series
• Manufacturer: Renesas Electronics Corporation.

Fig. 17.4.2 Example of program runaway detection using out-of-address-area detection mode
17.4.2 Operations in out-of-address-area detection mode
When an address matching detection interrupt request has been accepted, the interrupt disable flag (I) is
set to “1”; the processor interrupt priority level (IPL) does not change.
By setting the start address of the programming area into the address compare register 0 and the last
address of the programming area into the address compare register 1, a program runaway (in other words,
fetching op codes from the area out of the programming area) can be detected. If any program runaway
is detected and reset of the microcomputer is required, be sure to write “1” into the software reset bit (bit
6 at address 5E
Figure 17.4.2 shows an example of program runaway detection using the out-of-address-area detection
mode.
Setting the detect enable bit to “1” initiate to compare the contents of PG and PC with the contents of
The contents of PG, PC, and PS at acceptance of the address matching detection interrupt request are
the address compare registers 0 and 1.
When an address less than the contents of the address compare registers 0 or larger than the one of
the address compare register 1 is detected, an address matching detection interrupt request occurs, and
then, this request will be accepted.
Perform the necessary processing with an address matching detection interrupt routine.
saved onto the stack area. Therefore, be sure to rewrite the above contents of PG and PC to a certain
return address, and return there by using the RTI instruction.
END PRG
TOP PRG
FFFFFF
000000
TOP_PRG : Start address of programming area
END_PRG : Last address of programming area
Note: A program runaway may affect the contents of the data bank register (DT), the direct page registers (DPRi) etc.
addressing mode using DT, DPRi, etc.
Therefore, the contents of these registers must be rewritten in order to write “1” to the software reset bit with an
16
16
Programming area
16
) within an address matching detection interrupt routine.
Access to the area
out of the progra-
mming area
Access to the
area out of the
programming
area
7905 Group User’s Manual Rev.1.0
This address is to be set into the address compare register 1,
in advance.
This address is to be set into the address compare register 0,
in advance.
17.4 Out-of-address-area detection mode
Address matching detection
Software reset bit
(bit 6 at address 5E
interrupt routine
RTI
DEBUG FUNCTION
16
1
)
(Note)
The microcomputer
is reset
17-11