Zilog Z8F0130 Uživatelský manuál stáhnout pdf (Strana 46)

eZ8

™

CPU Core

User Manual

UM012820-0810 Interrupts

Nesting of Vectored Interrupts

Vectored interrupt nesting allows higher priority requests to interrupt a

lower priority request. To initiate vectored interrupt nesting, follow the

steps below, during the interrupt service routine:

1. Push the old Interrupt Control and Interrupt Enable Register

information about the stack.

2. Load the Interrupt Enable Register information with new masks to

disable lower priority interrupts.

3. Execute an EI instruction to enable the interrupts.

4. Proceed with the interrupt service routine processing.

5. After processing is complete, execute a DI instruction to disable the

interrupts.

6. Restore the Interrupt Control and Interrupt Enable Register

information from the stack.

7. Execute an IRET instruction to return from the interrupt service

routine.

Polled Interrupt Processing

Polled interrupt processing is supported by individually disabling the

interrupts to be polled. To initiate polled processing, check the interrupt

bits of interest in the Interrupt Request Register(s) using the Test Under

Mask (TM) or similar bit test instruction. If the bit is 1, perform a

software call or branch to the interrupt service routine. Write the service

routine to service the request, reset the Interrupt Request bit in the

Interrupt Request Register, and return or branch back to the main

program. An example of a polling routine follows:

TM IRQ1, #0010000b; Test for

interrupt request in bit 5 of IRQ1

1 2 ... 41 42 43 44 45 46 47 48 49 50 51 ... 313 314

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Zilog Z8F0130 Uživatelský manuál Strana 46