MC9S12HY64 Datasheet, PDF (193/792 Pages) Freescale Semiconductor, Inc – S12 Microcontrollers

S12S Debug Module (S12SDBGV2)
6.3.2.6 Debug Count Register (DBGCNT)
Address: 0x0026
7
6
5
4
3
2
1
0
R TBF
0
CNT
W
Reset
—
—
—
—
—
—
—
—
POR
0
0
0
0
0
0
0
0
= Unimplemented or Reserved
Figure 6-8. Debug Count Register (DBGCNT)
Read: Anytime
Write: Never
Table 6-12. DBGCNT Field Descriptions
Field
Description
7
TBF
5–0
CNT[5:0]
Trace Buffer Full — The TBF bit indicates that the trace buffer has stored 64 or more lines of data since it was
last armed. If this bit is set, then all 64 lines will be valid data, regardless of the value of DBGCNT bits. The TBF
bit is cleared when ARM in DBGC1 is written to a one. The TBF is cleared by the power on reset initialization.
Other system generated resets have no affect on this bit
This bit is also visible at DBGSR[7]
Count Value — The CNT bits indicate the number of valid data 20-bit data lines stored in the Trace Buffer.
Table 6-13 shows the correlation between the CNT bits and the number of valid data lines in the Trace Buffer.
When the CNT rolls over to zero, the TBF bit in DBGSR is set and incrementing of CNT will continue in
end-trigger mode. The DBGCNT register is cleared when ARM in DBGC1 is written to a one. The DBGCNT
register is cleared by power-on-reset initialization but is not cleared by other system resets. Thus should a reset
occur during a debug session, the DBGCNT register still indicates after the reset, the number of valid trace buffer
entries stored before the reset occurred. The DBGCNT register is not decremented when reading from the trace
buffer.
Table 6-13. CNT Decoding Table
TBF
CNT[5:0]
0
000000
0
000001
000010
000100
000110
..
111111
1
000000
1
000001
..
..
111110
Description
No data valid
1 line valid
2 lines valid
4 lines valid
6 lines valid
..
63 lines valid
64 lines valid; if using Begin trigger alignment,
ARM bit will be cleared and the tracing session ends.
64 lines valid,
oldest data has been overwritten by most recent data
MC9S12HY/HA-Family Reference Manual, Rev. 1.04
Freescale Semiconductor
193