st20-gp6 STMicroelectronics, st20-gp6 Datasheet - Page 37

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

6
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
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
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
0
1
2
3
15:4
16
17
Interrupt level controller
Interrupt assignments
Interrupt level controller registers
Peripheral
PIO A
PIO B
ASC0
ASC1
UNUSED
Interrupt0 pin
Interrupt1 pin
Signals ORed together to generate interrupt signal
Compare function
Compare function
ASC0TxBufEmpty, ASC0TxEmpty, ASC0RxBufFull, ASC0ErrorInterrupt
ASC1TxBufEmpty, ASC1TxEmpty, ASC1RxBufFull, ASC1ErrorInterrupt
UNUSED
Table 6.1 Interrupt assignments
ST20-GP6
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