MC9S12HZ256 Datasheet, PDF (546/692 Pages) Freescale Semiconductor, Inc – HCS12 Microcontrollers

Chapter 19 Debug Module (DBGV1)
19.3.2.4 Debug Count Register (DBGCNT)
R
W
Reset
Field
7
TBF
5:0
CNT
7
6
5
4
3
2
1
0
TBF
0
CNT
0
0
0
0
0
0
0
0
= Unimplemented or Reserved
Figure 19-8. Debug Count Register (DBGCNT)
Table 19-8. DBGCNT Field Descriptions
Description
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.
Count Value — The CNT bits indicate the number of valid data words stored in the trace buffer. Table 19-9 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 19-9. CNT Decoding Table
TBF
CNT
Description
0
000000
0
000001
No data valid
1 word valid
0
000010
..
..
111110
0
111111
2 words valid
..
..
62 words valid
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
64 words valid,
..
oldest data has been overwritten
..
by most recent data
111111
MC9S12HZ256 Data Sheet, Rev. 2.04
546
Freescale Semiconductor