ARM Cortex-M3 Technical Reference Manual page 90

Exceptions
Exception type
Debug Monitor
-
PendSV
SysTick
External Interrupt
a. You can change this priority of this exception, See System Handler Priority Registers bit assignments on page 8-27. Settable
is an NVIC priority value of 0 to N, where N is the largest priority value implemented. Internally, the highest user-settable
priority (0) is treated as 4.
b. You can enable or disable this fault. See System Handler Control and State Register bit assignments on page 8-28.
5-4
Position Priority
12 settable
13 -
14 settable
15 settable
16 and above settable
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Description
Debug monitor, when not halting. This is synchronous, but
only active when enabled. It does not activate if lower priority
than the current activation.
Reserved
Pendable request for system service. This is asynchronous and
only pended by software.
System tick timer has fired. This is asynchronous.
Asserted from outside the core, INTISR[239:0], and fed
through the NVIC (prioritized). These are all asynchronous.
Table 5-1 Exception types
ARM DDI 0337B