DEBUG FUNCTION
17.1 Overview, 17.2 Block description
17.1 Overview
When the CPU fetches an op code (op-code fetch), the debug function generates an address matching
detection interrupt request if a selected condition is satisfied as a result of comparison between the address
where the op code to be fetched is stored (in other words, the contents of PG and PC) and the specified
address.
The debug function provides the following 2 modes:
(1) Address matching detection mode
When the contents of PG and PC match with the specified address, an address matching detection
interrupt request occurs. This mode can be used for avoiding or modifying a portion of a program.
(2) Out-of-address-area detection mode
When the contents of PG and PC go out of the specified area, an address matching detection interrupt
request occurs. This mode can be used for the program runaway detection by specifying the area
where a program exists.
Note that an address matching detection interrupt is a non-maskable software interrupt. For details of this
interrupt, refer to “CHAPTER 6. INTERRUPTS.”
In addition, the debug function cannot be evaluated by a debugger. Therefore, do not use a debugger when
using the debug function.
17.2 Block description
Figure 17.2.1 shows the block diagram of the debug function, and the registers relevant to this function are
described in the following.
Internal data bus (DB0 to DB15
)
Debug control register 0
Debug control register 1
Address compare register 0
Address compare register 1
Address matching
detect circuit
Address matching
detection interrupt
Matching • Compare register
Matching • Compare register
CPU bus (Address)
Fig. 17.2.1 Block diagram of debug function
7905 Group User’s Manual Rev.1.0
17-2
RENESAS [ RENESAS TECHNOLOGY CORP ]
