Specifications

Table Of Contents
ARM Debugger 110 ARM specific SYStem Commands
©1989-2014 Lauterbach GmbH
sequence is only possible while nTRST is inactive. In the following figure the marked time between the
deassertion of reset and the entry into debug mode is the time of this JTAG sequence plus a time delay
selectable by SYStem.Option WaitReset (default = 3 msec).
If nTRST is available and not connected to nRESET/nSRST it is possible to force the CPU directly after
reset (without cycles) into debug mode. This is also possible by pulling nTRST fixed to VCC (inactive), but
then there is the problem that it is normally not ensured that the JTAG port is reset in normal operation. If the
ResBreak option is enabled the debugger first deasserts nTRST, then it executes a JTAG sequence to set
the DBGRQ bit in the ICE breaker control register and then it deasserts nRESET/nSRST.
SYStem.Option ResetDetection Choose method to detect a target reset
Default: nSRST
Selects the method how an external target reset can be detected by the debugger.
Format: SYStem.Option ResetDetection <method>
<method>: nSRST | None
nSRST Detects a reset if nSRST (nRESET) line on the debug connector is pulled
low.
None Detection of external resets is disabled.
nTRST
nSRST
CPU State
reset running debug
nTRST
nSRST
CPU State
reset debug