st20-gp1 STMicroelectronics, st20-gp1 Datasheet - Page 23

• Manufacturer Part Number: st20-gp1
• Description: Gps Processor
• Manufacturer: STMicroelectronics

4.6
A software error, such as arithmetic overflow or array bounds violation, can cause an error flag to
be set in the CPU. The flag is directly connected to the ErrorOut pin. Both the flag and the pin can
be ignored, or the CPU stopped. Stopping the CPU on an error means that the error cannot cause
further corruption. As well as containing the error in this way it is possible to determine the state of
the CPU and its memory at the time the error occurred. This is particularly useful for postmortem
debugging where the debugger can be used to examine the state and history of the processor
leading up to and causing the error condition.
In addition, if a trap handler process is installed, a variety of traps/exceptions can be trapped and
handled by software. A user supplied trap handler routine can be provided for each high/low
process priority level. The handler is started when a trap occurs and is given the reason for the
trap. The trap handler is not re-entrant and must not cause a trap itself within the same group. All
traps are individually maskable.
4.6.1
The trap mechanism is arranged on a per priority basis. For each priority there is a handler for each
group of traps, as shown in Figure 4.4.
ClockReg0
TptrReg0
TnextReg0
Traps and exceptions
Trap groups
comparator
21
5
Figure 4.3 Timer registers
Alarm
Workspaces
Empty
31
21
Program
ST20-GP1
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