PC912XDP512F0MPVR datasheet(712/1348 Pages) FREESCALE

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Chapter 19 S12X Debug (S12XDBGV2) Module

MC9S12XDP512 Data Sheet, Rev. 2.21

714

Freescale Semiconductor

19.3.1.11.8

Debug Comparator Data Low Mask Register (DBGXDLM)

Read: Anytime

Write: Anytime when DBG not armed.

19.4

Functional Description

This section provides a complete functional description of the DBG module. If the part is in secure mode,

the DBG module can generate breakpoints but tracing is not possible.

19.4.1

DBG Operation

Arming the DBG module by setting ARM in DBGC1 allows triggering, and storing of data in the trace

buffer and can be used to cause breakpoints to the CPU or the XGATE module. The DBG module is made

up of 4 main blocks, the comparators, control logic, the state sequencer and the trace buffer.

The comparators monitor the bus activity of the CPU and XGATE modules. Comparators can be

conﬁgured to monitor address and databus. Comparators can also be conﬁgured to mask out individual

data bus bits during a compare and to use R/W and word/byte access qualiﬁcation in the comparison. When

a match with a comparator register value occurs the associated control logic can trigger the state sequencer

to another state (Figure 19-23). Either forced or tagged triggers are possible. Using a forced trigger, the

trigger is generated immediately on a comparator match. Using a tagged trigger, at a comparator match,

the instruction opcode is tagged and only if the instruction reaches the execution stage of the instruction

queue is a trigger generated. In the case of a transition to ﬁnal state, bus tracing is triggered and/or a

breakpoint can be generated. Tracing of both CPU and/or XGATE bus activity is possible.

Independent of the state sequencer, a breakpoint can be triggered by the external TAGHI / TAGLO signals,

by an XGATE S/W breakpoint request or by writing to the TRIG bit in the DBGC1 control register.

The trace buffer is visible through a 2-byte window in the register address map and can be read out using

standard 16-bit word reads.

0x002F

76543210

Bit 7

Bit 0

Reset

00000000

Figure 19-21. Debug Comparator Data Low Mask Register (DBGXDLM)

Table 19-35. DBGXDLM Field Descriptions

Field

Description

7–0

Bits [7:0]

Comparator Data Low Mask Bits — The comparator data low mask bits control whether the selected

comparator compares the data bus bits [7:0] to the corresponding comparator data compare bits. This register

is available only for comparators A and C.

0 Do not compare corresponding data bit

1 Compare corresponding data bit

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