142
JTAG Circuitry for Debug
11.4
JTAG Hardware Requirements
Due to the conflicting requirements of Multi-ICE* and the Intel XScale
®
microarchitecture, it is
necessary to incorporate a circuit that can drive
TRST#
low at power up and weakly pull it high at
all other times. The following section details the circuits required for the Macraigor Raven*,
WindRiver Systems* visionPROBE* / visionICE*, and ARM* Multi-ICE*.
11.4.1
Macraigor Raven and WindRiver Systems visionPROBE /
visionICE
Both the Macraigor Raven and WindRiver Systems visionPROBE / visionICE (when configured as
active) do not require any special power-up circuitry. The requirement is that nTRST is weakly
pulled down at the processor. It is suggested that the value of the pull-down resistor is 10 K
Ω
or
greater. The value of this resistor needs to be confirmed with the JTAG debugger manufacturer to
ensure optimal performance.
11.4.2
ARM Multi-ICE
The ARM Multi-ICE debugger requires special power-up circuitry due to the open collector
implementation of the nTRST signal. This power-up circuit must ensure that nTRST is asserted
(low) at power on and weakly pulled high thereafter. Refer to
for the example of the
Power-Up Circuit for nTRST.
Figure 74.
Example Power-Up Circuit for nTRST
A9286-01
0.01µF
MR#
RESET#
VCC
GND
220
Ω
nTRST
nTRST-DGB
1 k
Ω
3
4
1
2
3.3 V
3.3 V
MAX811S
Summary of Contents for 80331
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