Datasheet

Chapter 8 S12X Debug (S12XDBGV3) Module
MC9S12XE-Family Reference Manual Rev. 1.25
316 Freescale Semiconductor
8.3.2.6 Debug Count Register (DBGCNT)
Read: Anytime
Write: Never
Address: 0x0026
76543210
R 0 CNT
W
Reset
POR
0
0
—
0
—
0
—
0
—
0
—
0
—
0
—
0
= Unimplemented or Reserved
Figure 8-8. Debug Count Register (DBGCNT)
Table 8-19. DBGCNT Field Descriptions
Field Description
6–0
CNT[6:0]
Count Value — The CNT bits [6:0] indicate the number of valid data 64-bit data lines stored in the Trace Buffer.
Table 8-20 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 or mid-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 8-20. CNT Decoding Table
TBF (DBGSR) CNT[6:0] Description
0 0000000 No data valid
0 0000001 32 bits of one line valid
(1)
1. This applies to Normal/Loop1/PurePC Modes when tracing from either CPU12X or XGATE only.
0 0000010
0000100
0000110
..
1111100
1 line valid
2 lines valid
3 lines valid
..
62 lines valid
0 1111110 63 lines valid
1 0000000 64 lines valid; if using Begin trigger alignment,
ARM bit will be cleared and the tracing session ends.
1 0000010
..
..
1111110
64 lines valid,
oldest data has been overwritten by most recent data