P912XDP512F0MFVR datasheet(715/1350 Pages) FREESCALE

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Chapter 19 Debug (S12XDBGV2)

MC9S12XDP512 Data Sheet, Rev. 2.17

Freescale Semiconductor

715

Figure 19-22. DBG Overview

19.4.2

Comparator Modes

The DBG contains 4 comparators, A, B, C, and D. Each comparator can be conﬁgured to monitor either

CPU or XGATE busses using the SRC bit in the corresponding comparator control register. Each

comparator compares the selected address bus with the address stored in DBGXAH, DBGXAM and

DBGXAL. Furthermore comparators A and C also compare the data buses to the data stored in DBGXDH,

DBGXDL and allow masking of individual data bus bits.

All comparators are disabled in BDM and during BDM accesses.

The comparator match control logic (see Figure 19-22) conﬁgures comparators to monitor the busses for

an exact address or an address range, whereby either an access inside or outside the speciﬁed range

generates a match condition. The comparator conﬁguration is controlled by the control register contents

and the range control by the DBGC2 contents.

On a match a trigger can initiate a transition to another state sequencer state (see Section 19.4.3, “Trigger

Modes”). The comparator control register also allows the type of access to be included in the comparison

through the use of the RWE,RW,SZE and SZ bits. The RWE bit controls whether read or write comparison

is enabled for the associated comparator and the RW bit selects either a read or write access for a valid

match. Similarly the SZE and SZ bits allows the size of access (word or byte) to be considered in the

compare. Only comparators B and D feature SZE and SZ.

The TAG bit in each comparator control register is used to determine the triggering condition. By setting

TAG, the comparator will qualify a match with the output of opcode tracking logic and a trigger occurs

before the tagged instruction executes (tagged-type trigger). Whilst tagging the RW, RWE, SZE and SZ

bits are ignored and the comparator register must be loaded with the exact opcode address.

CPU BUS

TRIGGER

EXTERNAL TAGHI / TAGLO

MATCH0

XGATE BUS

COMPARATOR B

COMPARATOR C

COMPARATOR D

COMPARATOR A

MATCH1

MATCH2

MATCH3

READ TRACE DATA (DBG READ DATA BUS)

SECURE

BREAKPOINT REQUESTS

XGATE S/W BREAKPOINT REQUEST

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