Datasheet

Chapter 16 Debug Module (DBGV1)
MC9S12E128 Data Sheet, Rev. 1.07
484 Freescale Semiconductor
16.3.2.4 Debug Count Register (DBGCNT)
76543210
R TBF 0 CNT
W
Reset 0 0 0 00000
= Unimplemented or Reserved
Figure 16-8. Debug Count Register (DBGCNT)
Table 16-8. DBGCNT Field Descriptions
Field Description
7
TBF
Trace Buffer Full — The TBF bit indicates that the trace buffer has stored 64 or more words of data since it was
last armed. If this bit is set, then all 64 words will be valid data, regardless of the value in CNT[5:0]. The TBF bit
is cleared when ARM in DBGC1 is written to a 1.
5:0
CNT
Count Value — The CNT bits indicate the number of valid data words stored in the trace buffer. Table 16-9 shows
the correlation between the CNT bits and the number of valid data words in the trace buffer. When the CNT rolls
over to 0, the TBF bit will be set and incrementing of CNT will continue if DBG is in end-trigger mode. The
DBGCNT register is cleared when ARM in DBGC1 is written to a 1.
Table 16-9. CNT Decoding Table
TBF CNT Description
0 000000 No data valid
0 000001 1 word valid
0 000010
..
..
111110
2 words valid
..
..
62 words valid
0 111111 63 words valid
1 000000 64 words valid; if BEGIN = 1, the
ARM bit will be cleared. A
breakpoint will be generated if
DBGBRK = 1
1 000001
..
..
111111
64 words valid,
oldest data has been overwritten
by most recent data