SH7055S Datasheet, PDF (165/1002 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperH RISC engine Family/SH7000 Series

8.3 Operation
8.3.1 Flow of the User Break Operation
The flow from setting of break conditions to user break interrupt exception processing is described
below:
1. The user break addresses are set in the user break address register (UBAR), the desired masked
bits in the addresses are set in the user break address mask register (UBAMR) and the breaking
bus cycle type is set in the user break bus cycle register (UBBR). If even one of the three
groups of the UBBR’s CPU cycle/DMA cycle select bits (CP1, CP0), instruction fetch/data
access select bits (ID1, ID0), and read/write select bits (RW1, RW0) is set to 00 (no user break
generated), no user break interrupt will be generated even if all other conditions are in
agreement. When using user break interrupts, always be certain to establish bit conditions for
all of these three groups.
2. The UBC uses the method shown in figure 8.2 to judge whether set conditions have been
fulfilled. When the set conditions are satisfied, the UBC sends a user break interrupt request
signal to the interrupt controller (INTC). At the same time, a condition match signal is output
at the UBCTRG pin with the pulse width set in bits CKS1 and CKS0.
3. The interrupt controller checks the accepted user break interrupt request signal’s priority level.
The user break interrupt has priority level 15, so it is accepted only if the interrupt mask level
in bits I3–I0 in the status register (SR) is 14 or lower. When the I3–I0 bit level is 15, the user
break interrupt cannot be accepted but it is held pending until user break interrupt exception
processing can be carried out. Consequently, user break interrupts within NMI exception
service routines cannot be accepted, since the I3–I0 bit level is 15. However, if the I3–I0 bit
level is changed to 14 or lower at the start of the NMI exception service routine, user break
interrupts become acceptable thereafter. See section 7, Interrupt Controller (INTC), describes
the handling of priority levels in greater detail.
4. The INTC sends the user break interrupt request signal to the CPU, which begins user break
interrupt exception processing upon receipt. See section 7.4, Interrupt Operation, for details on
interrupt exception processing.
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