Chapter 20 S12X Debug (S12XDBGV3) Module
MC9S12XDP512 Data Sheet, Rev. 2.17
778
Freescale Semiconductor
20.4.5.3
Trace Buffer Organization
The buffer can be used to trace either from S12XCPU, from XGATE or from both sources. An X prex
denotes information from the XGATE module, a C prex denotes information from the S12XCPU.
ADRH, ADRM, ADRL denote address high, middle and low byte respectively. INF bytes contain control
information (R/W, S/D etc.). The numerical sufx indicates which tracing step. The information format
for Loop1 Mode is the same as that of Normal Mode. Whilst tracing from XGATE or S12XCPU only, in
Normal or Loop1 modes each array line contains data from entries made at two separate times, thus in this
case the DBGCNT[0] is incremented after each separate entry. In all other modes DBGCNT[0] remains
cleared whilst the other DBGCNT bits are incremented on each trace buffer entry.
XGATE and S12XCPU COFs occur independently of each other and the prole of COFs for the two
sources is totally different. When both sources are being traced in Normal or Loop1 mode, for each COF
from one source, there may be many COFs from the other source, depending on user code. COF events
could occur far from each other in the time domain, on consecutive cycles or simultaneously. When a COF
occurs in either source (S12X or XGATE) a trace buffer entry is made and the corresponding CDV or XDV
bit is set. The current PC of the other source is simultaneously stored to the trace buffer even if no COF
has occurred, in which case CDV/XDV remains cleared indicating the address is not associated with a
COF, but is simply a snapshot of the PC contents at the time of the COF from the other source.
Single byte data accesses in Detail Mode are always stored to the low byte of the trace buffer (CDATAL
or XDATAL) and the high byte is cleared. When tracing word accesses, the byte at the lower address is
always stored to trace buffer byte3 and the byte at the higher address is stored to byte2
Table 20-39. Trace Buffer Organization
Mode
8-Byte Wide Word Buffer
76543210
XGATE
Detail
CXINF1
CADRH1
CADRM1
CADRL1
XDATAH1
XDATAL1
XADRM1
XADRL1
CXINF2
CADRH2
CADRM2
CADRL2
XDATAH2
XDATAL2
XADRM2
XADRL2
S12XCPU
Detail
CXINF1
CADRH1
CADRM1
CADRL1
CDATAH1
CDATAL1
XADRM1
XADRL1
CXINF2
CADRH2
CADRM2
CADRL2
CDATAH2
CDATAL2
XADRM2
XADRL2
Both
Other Modes
XINF0
XPCM0
XPCL0
CINF0
CPCH0
CPCM0
CPCL0
XINF1
XPCM1
XPCL1
CINF1
CPCH1
CPCM1
CPCL1
XGATE
Other Modes
XINF1
XPCM1
XPCL1
XINF0
XPCM0
XPCL0
XINF3
XPCM3
XPCL3
XINF2
XPCM2
XPCL2
S12XCPU
Other Modes
CINF1
CPCH1
CPCM1
CPCL1
CINF0
CPCH0
CPCM0
CPCL0
CINF3
CPCH3
CPCM3
CPCL3
CINF2
CPCH2
CPCM2
CPCL2