st20-gp6 STMicroelectronics, st20-gp6 Datasheet - Page 31

• Manufacturer Part Number: st20-gp6
• Description: Gps Processor
• Manufacturer: STMicroelectronics

Interrupts on the ST20-GP6 are implemented via an on-chip interrupt controller peripheral. An
interrupt can be signalled to the controller by one of the following:
5.1
The interrupt controller contains a table of pointers to interrupt handlers. Each interrupt handler is
represented by its workspace pointer (Wptr). The table contains a workspace pointer for each level
of interrupt.
The Wptr gives access to the code, data and interrupt save space of the interrupt handler. The
position of the Wptr in the interrupt table implies the priority of the interrupt.
Run-time library support is provided for setting and programming the vector table.
5.2
At any interruptible point in its execution the CPU can receive an interrupt request from the inter-
rupt controller. The CPU immediately acknowledges the request.
In response to receiving an interrupt the CPU performs a procedure call to the process in the vec-
tor table. The state of the interrupted process is stored in the workspace of the interrupt handler as
shown in Figure 5.2. Each interrupt level has its own workspace.
•
•
•
Wptr
a signal on an external Interrupt pin
a signal from an internal peripheral or subsystem
software asserting an interrupt in the Pending register
Interrupt vector table
Interrupt handlers
Before interrupt
Handler Status
Handler Iptr
Figure 5.2 State of interrupted process
Wptr
Interrupting high priority
Handler Status
Handler Iptr
process
Status
Creg
Breg
Areg
Wptr
Iptr
Wptr
Interrupting low priority
process or CPU idle
Handler Status
Handler Iptr
Null Status
ST20-GP6
31/123