I/O Diagrams For Dstream-Pt Signals; Figure 1-12 Input/Output Signals; Figure 1-13 Tck Signal; Figure 1-14 Reset Signals - ARM DSTREAM-PT Reference Manual

1.8

I/O diagrams for DSTREAM-PT signals

The following diagrams and descriptions illustrate a simplified view of how each signal type is
connected within the debug unit.
All comparator inputs have an indeterminate band of 100mV above, and below, VTREF/2. Signals that
are output from the target system, when passing through this voltage region, must be monotonic.
Input/Output signals
Standard input/output signals (TDI, TMS, TDO, RTCK, SWDIO, DBGRQ, DBGACK) use LVCMOS
output buffers and comparator inputs with a series 33Ω resistor.
TCK signal
The TCK output signal is similar to a standard output signal, but also has a switchable capacitor, forming
a T-filter, which can reduce the TCK slew-rate.
Enabling this filter is not currently supported in Arm Development Studio.
Reset signals
The reset signals (nSRST and nTRST) are similar to the standard input/output signals. However, they
have an extra LVCMOS driver, which is connected using a 4K7 resistor, that provides the weak pull-up
and pull-down functionality.
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Note
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1 Debug and trace interface
1.8 I/O diagrams for DSTREAM-PT signals
33R
VTREF/2

Figure 1-12 Input/Output signals

16.5R 16.5R
220pF

Figure 1-13 TCK signal

33R
4K7
VTREF/2

Figure 1-14 Reset signals

Strong Driver
Weak Driver
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