ST20-GP6 datasheet(37/123 Pages) STMICROELECTRONICS

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ST20-GP6

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Interrupt level controller

There are 6 interrupts (of which 2 are external) generated in the ST20-GP6 system and each of

these is assigned to one of the interrupt controller’s 8 inputs. Thus each of the interrupt controller’s

inputs responds to zero or more of the 8 system interrupts.

An interrupt handler routine is able to ascertain the source of an interrupt where two or more sys-

tem interrupts are assigned to one handler by doing a device read from the

InputInterrupts regis-

ter (see Table 6.3) and examining the bits that correspond to the system interrupts assigned to that

handler.

The interrupt level controller has additional functionality to support the low power controller. The

external interrupts are monitored and a signal is generated for the low power controller which tells it

when any of them goes to a pre-determined level. This level is programmable for each external

interrupt, and in addition each interrupt can be selectively masked.

6.1

Interrupt assignments

The interrupts from the peripherals on the ST20-GP6 are assigned as follows:

These interrupts are inputs to the interrupt level controller. This allows these interrupts to be

assigned to any of eight interrupt priority levels and for multiple interrupts to share a priority level.

6.2

Interrupt level controller registers

The interrupt level controller is programmable via conﬁguration registers. These registers can be

examined and set by the

devlw (device load word) and devsw (device store word) instructions.

IntPriority registers

The priority assigned to each of the input interrupts is programmable via the

IntPriority registers.

The interrupt level controller asserts interrupt output

N when one or more of the input interrupts

with programmed priority equal to

N are high. It is level sensitive and re-timed at the input, thus

incurring one cycle of latency.

Interrupt Peripheral

Signals ORed together to generate interrupt signal

PIO A

Compare function

PIO B

Compare function

ASC0

ASC0TxBufEmpty, ASC0TxEmpty, ASC0RxBufFull, ASC0ErrorInterrupt

ASC1

ASC1TxBufEmpty, ASC1TxEmpty, ASC1RxBufFull, ASC1ErrorInterrupt

15:4

UNUSED

Interrupt0 pin

Interrupt1 pin

Table 6.1 Interrupt assignments

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