UM10429
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User manual
Rev. 1 — 20 October 2010
174 of 258
NXP Semiconductors
UM10429
Chapter 18: LPC1102 Serial Wire Debug (SWD)
18.6 Debug notes
18.6.1 Debug limitations
Important:
The user should be aware of certain limitations during debugging. The most
important is that, due to limitations of the ARM Cortex-M0 integration, the LPC1102
cannot wake up in the usual manner from Deep-sleep mode. It is recommended not to
use this mode during debug.
Another issue is that debug mode changes the way in which reduced power modes work
internal to the ARM Cortex-M0 CPU, and this ripples through the entire system. These
differences mean that power measurements should not be made while debugging, the
results will be higher than during normal operation in an application.
During a debugging session, the System Tick Timer is automatically stopped whenever
the CPU is stopped. Other peripherals are not affected.
18.6.2 Debug connections
The VTREF pin on the SWD connector enables the debug connector to match the target voltage.
Fig 34. Connecting the SWD pins to a standard SWD connector
RESET
Signals from SWD connector
SWDIO
SWCLK
VDD
Gnd
VTREF
SWDIO
SWCLK
nSRST
GND
LPC1102