ST20-GP1 datasheet(32/116 Pages) STMICROELECTRONICS

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ST20-GP1

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On start-up, the Mask register is initialized to zero’s, thus all interrupts are disabled, both globally

and individually. When a 1 is written to the GlobalEnable bit, the individual interrupt bits are still

disabled and must also have a 1 individually written to the InterruptEnable bit to enable the

respective interrupt.

The Mask register is mapped onto two additional addresses so that bits can be set or cleared

individually.

Set_Mask (address ‘interrupt base address + #C4’) allows bits to be set individually. Writing a ‘1’ in

this register sets the corresponding bit in the Mask register, a ‘0’ leaves the bit unchanged.

Clear_Mask (address ‘interrupt base address + #C8’) allows bits to be cleared individually. Writing

a ‘1’ in this register resets the corresponding bit in the Mask register, a ‘0’ leaves the bit

unchanged.

Pending register

The Pending register contains a bit per interrupt with each bit controlled by the corresponding

interrupt. A read can be used to examine the state of the interrupt controller while a write can be

used to explicitly trigger an interrupt.

A bit is set when the triggering condition for an interrupt is met. All bits are independent so that

several bits can be set in the same cycle. Once a bit is set, a further triggering condition will have

no effect. The triggering condition is independent of the Mask register.

The highest priority interrupt bit is reset once the interrupt controller has made an interrupt request

to the CPU.

Mask

Interrupt controller base address + #C0

Read/Write

Bit

Bit field

Function

Interrupt0Enable

When set to 1, interrupt 0 is enabled. When 0, interrupt 0 is disabled.

Interrupt1Enable

When set to 1, interrupt 1 is enabled. When 0, interrupt 1 is disabled.

Interrupt2Enable

When set to 1, interrupt 2 is enabled. When 0, interrupt 2 is disabled.

Interrupt3Enable

When set to 1, interrupt 3 is enabled. When 0, interrupt 3 is disabled.

Interrupt4Enable

When set to 1, interrupt 4 is enabled. When 0, interrupt 4 is disabled.

GlobalEnable

When set to 1, the setting of the interrupt is determined by the speciﬁc InterruptEn-

able bit. When 0, all interrupts are disabled.

15:5

RESERVED. Write 0.

Table 5.3 Mask register format

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