
Functional Description and Application Information
S12S Debug (S12SDBGV1) Module
MM912F634
Freescale Semiconductor
239
4.31.4.5.4
Trace Buffer Organization
ADRH, ADRM, and ADRL denote address high, middle, and low byte respectively. CRW and CSZ indicate R/W and size access
information. The numerical suffix refers to the tracing count. The information format for Loop1, Pure PC and Normal modes is
identical. In Detail mode, the address and data for each entry are stored on consecutive lines. Thus, the maximum number of
entries is 32. In this case, DBGCNT bits are incremented twice, once for the address line and once for the data line, on each
trace buffer entry.
Single byte data accesses in Detail mode is always stored to the low byte of the trace buffer (DATAL) and the high byte is cleared.
When tracing word accesses, the byte at the lower address is always stored to trace buffer byte1, and the byte at the higher
address is stored to byte0.
4.31.4.5.4.1
Information Bit Organization
The format of the bits is dependent upon the active trace mode, as described by the following.
4.31.4.5.4.2
Field2 Bits in Detail Mode
In Detail mode, the CSZ and CRW bits indicate the type of access being made by the CPU.
Table 312. Trace Buffer Organization(20-bit wide buffer)
Mode
Entry Number
4-bits
8-bits
Field 2
Field 1
Field 0
Detail Mode
Entry 1
CSZ1,CRW1,ADRH1
ADRM1
ADRL1
0
DATAH1
DATAL1
Entry 2
CSZ2,CRW2,ADRH2
ADRM2
ADRL2
0
DATAH2
DATAL2
Other Modes
Entry 1
PCH1
PCM1
PCL1
Entry 2
PCH2
PCM2
PCL2
Table 313. Field2 Information Bits in Detail Mode
Bit 3Bit 2Bit 1Bit 0
CSZ
CRW
ADRH17
ADRH16
Table 314. Field Descriptions
Field
Description
3
CSZ
Access Type Indicator— This bit indicates if the access was a byte or word size when tracing in Detail mode
0 Word Access
1 Byte Access
2
CRW
Read Write Indicator — This bit indicates if the corresponding stored address corresponds to a read or write access when
tracing in Detail Mode.
0 Write Access
1 Read Access
1
ADRH17
Address Bus bit 17— Corresponds to system address bus bit 17.
0
ADRH16
Address Bus bit 16— Corresponds to system address bus bit 16.