
MMDSP Debugger
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©1989-2019 Lauterbach GmbH
Electrical Description of the 20-pin Debug Cable
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The input and output signals are connected to a supply translating transceiver (74ALVC164245).
Therefore the ICD/AICD can work in an voltage range of (1.5 V) 1.8 … 3.3 V (3.6 V). Please note
that a 5 V supply environment is not supported! This would cause damage on the ICD/AICD.
Please contact us for alternate solutions if you need to work with 5 V.
•
VTREF is used as a sense line for the target voltage. It is also used as supply voltage for the
supply translating transceiver of the ICD/AICD interface to make an adaptation to the target
voltage (1.5 V) 1.8 … 3.3 V (3.6 V).
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nTRST, TDI, TMS, TCK are driven by the supply translating transceiver. In normal operation
mode this driver is enabled, but it can be disabled to give another tool access to the JTAG port. In
environments where multiple tools can access the JTAG port, it is absolutely required that there
is a pull down resistor at TCK. This is to ensure that TCK is low during a handover between
different tools.
•
TDO is an ICD/AICD input. It is connected to the supply translating transceiver.
•
nRSTIN is used by the debugger to reset the target CPU or to detect a reset on the target. It is
driven by an open collector buffer. A 47 k
pull-up resistor is included in the ICD/AICD connector.
The debugger will only assert a pulse on nSRST when the SYStem.UP, the SYStem.Mode Go or
the SYStem.RESetOUT command is executed. If it is ensured that the DSP is able to enter
debug mode every time (no hangup condition), the nSRST line is optional.
•
N/C (= Vsupply) is not connected in the ICD/AICD. This pin is used by debuggers of other
manufacturers for supply voltage input. The ICD/AICD is self-powered.
There is an additional plug in the connector on the debug cable to the debug interface. This signal is tristated
if the JTAG connector is tristated by the debugger and it is pulled low otherwise. This signal is normally not
required, but can be used to detect the tristate state if more than one debug tools are connected to the same
JTAG port.