SH7211 Datasheet, PDF (191/1228 Pages) Renesas Technology Corp – 32-Bit RISC Microcomputer SuperHTM RISC engine Family

Section 7 User Break Controller (UBC)
⎯ I bus cycles (including read fill cycles) resulting from instruction fetches on the C bus by
the CPU are defined as instruction fetch cycles on the I bus, while other bus cycles are
defined as data access cycles.
⎯ The DMAC only issues data access cycles for I bus cycles.
⎯ If a break condition is specified for the I bus, even when the condition matches in an I bus
cycle resulting from an instruction executed by the CPU, at which instruction the user
break is to be accepted cannot be clearly defined.
7.4.2 Break on Instruction Fetch Cycle
1. When C bus/instruction fetch/read/word or longword is set in the break bus cycle register
(BBR), the break condition is the FAB bus instruction fetch cycle. Whether PC breaks are set
before or after the execution of the instruction can then be selected with the PCB0 or PCB1 bit
of the break control register (BRCR) for the appropriate channel. If an instruction fetch cycle is
set as a break condition, clear LSB in the break address register (BAR) to 0. A break cannot be
generated as long as this bit is set to 1.
2. A break for instruction fetch which is set as a break before instruction execution occurs when it
is confirmed that the instruction has been fetched and will be executed. This means a break
does not occur for instructions fetched by overrun (instructions fetched at a branch or during
an interrupt transition, but not to be executed). When this kind of break is set for the delay slot
of a delayed branch instruction, the break is not generated until the execution of the first
instruction at the branch destination.
Note: If a branch does not occur at a delayed branch instruction, the subsequent instruction is
not recognized as a delay slot.
3. When setting a break condition for break after instruction execution, the instruction set with
the break condition is executed and then the break is generated prior to execution of the next
instruction. As with pre-execution breaks, a break does not occur with overrun fetch
instructions. When this kind of break is set for a delayed branch instruction and its delay slot,
the break is not generated until the first instruction at the branch destination.
4. When an instruction fetch cycle is set, the break data register (BDR) is ignored. Therefore,
break data cannot be set for the break of the instruction fetch cycle.
5. If the I bus is set for a break of an instruction fetch cycle, the setting is invalidated.
Rev. 2.00 May. 08, 2008 Page 167 of 1200
REJ09B0344-0200