SH7124 datasheet(155/782 Pages) RENESAS

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Section 7

User Break Controller (UBC)

Rev. 3.00

Sep. 27, 2007

Page 135 of 758

REJ09B0243-0300

7.3.2

Break on Instruction Fetch Cycle

1. When L bus/instruction fetch/read/word, longword, or not including the operand size is set in

the break bus cycle register (BBRA or BBRB), the break condition becomes the L bus

instruction fetch cycle. Whether it breaks before or after the execution of the instruction can

then be selected with the PCBA or PCBB bit in 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 (BARA or BARB) to 0. A break cannot be generated as long as this bit

is set to 1.

2. An instruction set for a break before execution breaks when it is confirmed that the instruction

has been fetched and will be executed. This means this feature cannot be used on 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 generated prior to execution of the delayed branch instruction.

Note:

If a branch does not occur at a delay condition branch instruction, the subsequent

instruction is not recognized as a delay slot.

3. When the condition is specified to be occur after execution, the instruction set with the break

condition is executed and then the break is generated prior to the execution of the next

instruction. As with pre-execution breaks, this cannot be used with overrun fetch instructions.

When this kind of break is set for a delayed branch instruction and its delay slot, a break is not

generated until the first instruction at the branch destination.

4. When an instruction fetch cycle is set, the break data register (BDRA or BDRB) 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 condition is determined for the

instruction fetch cycles on the I bus. For details, see 5 in section 7.3.1, Flow of the User Break

Operation.

7.3.3

Break on Data Access Cycle

1. If the L bus is specified as a break condition for data access break, condition comparison is

performed for the address (and data) accessed by the executed instructions, and a break occurs

if the condition is satisfied. If the I bus is specified as a break condition, condition comparison

is performed for the addresses (and data) of the data access cycles that are issued on the I bus

by all bus masters including the CPU, and a break occurs if the condition is satisfied. For

details on the CPU bus cycles issued on the I bus, see 5 in section 7.3.1, Flow of the User

Break Operation.

2. The relationship between the data access cycle address and the comparison condition for each

operand size is listed in table 7.2.

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