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UM10503
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© NXP B.V. 2012. All rights reserved.
User manual
Rev. 1.3 — 6 July 2012
1212 of 1269
NXP Semiconductors
UM10503
Chapter 48: LPC43xx JTAG, Serial Wire Debug (SWD), and trace
48.7 Debug Notes
The following limitations apply during debugging:
•
Due to limitations of the Cortex-M4 integration, the LPC43xx cannot wake up in the
usual manner from Deep Sleep and Power-down modes. It is recommended not to
use these modes during debug.
•
The debug mode changes the way in which reduced power modes are handled by the
Cortex-M4 CPU. This causes power modes at the device level to be different from
normal mode operation. 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 and the Repetitive Interrupt
Timers are automatically stopped whenever the CPU is stopped. Other peripherals
are not affected. If the Repetitive Interrupt Timer is configured such that its clock rate
is lower than the CPU clock rate, the RIT may not increment predictably during some
debug operations, such as single stepping.
•
Debugging is disabled if code read protection is enabled.
48.8 Debug memory re-mapping
Following chip reset, a portion of the Boot ROM is mapped to address 0 so that it will be
automatically executed. The Boot ROM switches the map to point to 0x1000 0000 or
0x1C00 0000 (when booting from EMC) or 0x8000 0000 (when booting from SPIFI). Code
execution can start from address 0x0000 0000 using the M4 memory mapping register
(
).
The register mapping is normally not transparent to the user. However, when a debugger
halts CPU execution immediately following reset, the Boot ROM is still mapped to address
0 and the IRC calibration value has not been loaded, which may cause the IRC frequency
to be outside of the specified 12 MHz. Ideally, the debugger should correct the mapping
automatically in this case.
48.9 JTAG TAP Identification
The JTAG TAP controller contains device ID that can be used by debugging software to
identify the general type of device.
Table 1082.JTAG TAP identification
Mode
ID code
JTAG mode
0x4BA0 0477
SWD mode
0x2BA0 1477
Cortex-M0 co-processor
0x0BA0 1477