SH7124 datasheet(154/782 Pages) RENESAS

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Section 7

User Break Controller (UBC)

Rev. 3.00

Sep. 27, 2007

Page 134 of 758

REJ09B0243-0300

7.3

Operation

7.3.1

Flow of the User Break Operation

The flow from setting of break conditions to user break exception processing is described below:

1. The break addresses are set in the break address registers (BARA or BARB). The masked

addresses are set in the break address mask registers (BAMRA or BAMRB). The break data is

set in the break data register (BDRA or BDRB). The masked data is set in the break data mask

registers (BBRA or BBRB). Three groups of BBRA or BBRB (L bus cycle/I bus cycle select,

instruction fetch/data access select, and read/write select) are each set. No user break will be

generated if even one of these groups is set with B'00. The respective conditions are set in the

bits of the break control register (BRCR). Make sure to set all registers related to breaks before

setting BBRA or BBRB.

2. When the break conditions are satisfied, the UBC sends a user break interrupt request to the

CPU and sets the L bus condition match flag (SCMFCA or SCMFCB) and the I bus condition

match flag (SCMFDA or SCMFDB) for the appropriate channel.

3. The appropriate condition match flags (SCMFCA, SCMFDA, SCMFCB, and SCMFDB) can

be used to check if the set conditions match or not. The matching of the conditions sets flags,

but they are not reset. Before using them again, 0 must first be written to them and then reset

flags.

4. There may be an occasion when a break condition match occurs both in channels A and B

around the same time. In this case, the flags for both conditions matches will be set even

though only one user-break interrupt request is issued to the CPU.

5. When selecting the I bus as the break condition, note the following:

 The CPU is connected to the I bus. The UBC monitors bus cycles generated by all bus

masters that are selected by the CPA2 to CPA0 bits in BBRA or the CPB2 to CPB0 bits in

BBRB, and compares the condition match.

 I bus cycles (including read fill cycles) resulting from instruction fetches on the L bus by

the CPU are defined as instruction fetch cycles on the I bus, while other bus cycles are

defined as data access 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.

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