ST20-GP1 datasheet(28/116 Pages) STMICROELECTRONICS

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ST20-GP1

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Interrupt controller

The ST20-GP1 supports external interrupts, enabling an on-chip subsystem or external interrupt

pin to interrupt the currently running process in order to run an interrupt handling process.

The ST20-GP1 interrupt subsystem supports ﬁve prioritized interrupts. This allows nested pre-

emptive interrupts for real-time system design. Three interrupts are connected to on-chip

peripherals (2 for the UARTs, 1 for the programmable IO) and two are available as external

interrupt pins.

All interrupts are at a higher priority than the high priority process queue, see Figure 5.1. Each

interrupt level has a higher priority than the previous (interrupt 0 is lowest priority) and each level

supports only one software handler process.Note that interrupt handlers must not prevent the GPS

DSP data trafﬁc from being handled. During continuous operation this has 1 ms latency and is not

a problem, but during initial acquisition it has a 32

µs rate and thus all interrupts must be disabled

except if used to stop GPS operation.

Figure 5.1 Interrupt priority

Interrupts on the ST20-GP1 are implemented via an on-chip interrupt controller peripheral. An

interrupt can be signalled to the controller by one of the following:

•

a signal on an external Interrupt pin

•

a signal from an internal peripheral or subsystem

•

software asserting an interrupt in a bit mask

Interrupt 3

Interrupt 1

Interrupt 0

High priority

Low priority

Increasing

pre-emption

process

Programmable IO

UART0

Interrupt 2

UART1

Interrupt0 pin

Interrupt 4

Interrupt1 pin

ST20-GP1 Datasheet(PDF) 28 Page - STMicroelectronics