Interrupt Handling

These interfaces contain definitions related to interrupt handling. They include definitions of exception and interrupt numbers, interrupt enabling and masking.

These definitions are normally found in cyg/hal/hal_intr.h. This file is supplied by the architecture HAL. Any variant or platform specific definitions will be found in cyg/hal/var_intr.h, cyg/hal/plf_intr.h or cyg/hal/hal_platform_ints.h in the variant or platform HAL, depending on the exact target. These files are include automatically by this header, so need not be included explicitly.

Vector numbers

CYGNUM_HAL_VECTOR_XXXX
CYGNUM_HAL_VSR_MIN
CYGNUM_HAL_VSR_MAX
CYGNUM_HAL_VSR_COUNT

CYGNUM_HAL_INTERRUPT_XXXX
CYGNUM_HAL_ISR_MIN
CYGNUM_HAL_ISR_MAX
CYGNUM_HAL_ISR_COUNT

CYGNUM_HAL_EXCEPTION_XXXX
CYGNUM_HAL_EXCEPTION_MIN
CYGNUM_HAL_EXCEPTION_MAX
CYGNUM_HAL_EXCEPTION_COUNT

All possible VSR, interrupt and exception vectors are specified here, together with maximum and minimum values for range checking. While the VSR and exception numbers will be defined in this file, the interrupt numbers will normally be defined in the variant or platform HAL file that is included by this header.

There are two ranges of numbers, those for the vector service routines and those for the interrupt service routines. The relationship between these two ranges is undefined, and no equivalence should be assumed if vectors from the two ranges coincide.

The VSR vectors correspond to the set of exception vectors that can be delivered by the CPU architecture, many of these will be internal exception traps. The ISR vectors correspond to the set of external interrupts that can be delivered and are usually determined by extra decoding of the interrupt controller by the interrupt VSR.

Where a CPU supports synchronous exceptions, the range of such exceptions allowed are defined by CYGNUM_HAL_EXCEPTION_MIN and CYGNUM_HAL_EXCEPTION_MAX. The CYGNUM_HAL_EXCEPTION_XXXX definitions are standard names used by target independent code to test for the presence of particular exceptions in the architecture. The actual exception numbers will normally correspond to the VSR exception range. In future other exceptions generated by the system software (such as stack overflow) may be added.

CYGNUM_HAL_ISR_COUNT, CYGNUM_HAL_VSR_COUNT and CYGNUM_HAL_EXCEPTION_COUNT define the number of ISRs, VSRs and EXCEPTIONs respectively for the purposes of defining arrays etc. There might be a translation from the supplied vector numbers into array offsets. Hence CYGNUM_HAL_XXX_COUNT may not simply be CYGNUM_HAL_XXX_MAX - CYGNUM_HAL_XXX_MIN or CYGNUM_HAL_XXX_MAX+1.

Interrupt state control

CYG_INTERRUPT_STATE
HAL_DISABLE_INTERRUPTS( old )
HAL_RESTORE_INTERRUPTS( old )
HAL_ENABLE_INTERRUPTS()
HAL_QUERY_INTERRUPTS( state )

These macros provide control over the state of the CPUs interrupt mask mechanism. They should normally manipulate a CPU status register to enable and disable interrupt delivery. They should not access an interrupt controller.

CYG_INTERRUPT_STATE is a data type that should be used to store the interrupt state returned by HAL_DISABLE_INTERRUPTS() and HAL_QUERY_INTERRUPTS() and passed to HAL_RESTORE_INTERRUPTS().

HAL_DISABLE_INTERRUPTS() disables the delivery of interrupts and stores the original state of the interrupt mask in the variable passed in the old argument.

HAL_RESTORE_INTERRUPTS() restores the state of the interrupt mask to that recorded in old.

HAL_ENABLE_INTERRUPTS() simply enables interrupts regardless of the current state of the mask.

HAL_QUERY_INTERRUPTS() stores the state of the interrupt mask in the variable passed in the state argument. The state stored here should also be capable of being passed to HAL_RESTORE_INTERRUPTS() at a later point.

It is at the HAL implementer’s discretion exactly which interrupts are masked by this mechanism. Where a CPU has more than one interrupt type that may be masked separately (e.g. the ARM's IRQ and FIQ) only those that can raise DSRs need to be masked here. A separate architecture specific mechanism may then be used to control the other interrupt types.

ISR and VSR management

HAL_INTERRUPT_IN_USE( vector, state )
HAL_INTERRUPT_ATTACH( vector, isr, data, object )
HAL_INTERRUPT_DETACH( vector, isr )
HAL_VSR_SET( vector, vsr, poldvsr )
HAL_VSR_GET( vector, pvsr )
HAL_VSR_SET_TO_ECOS_HANDLER( vector, poldvsr )

These macros manage the attachment of interrupt and vector service routines to interrupt and exception vectors respectively.

HAL_INTERRUPT_IN_USE() tests the state of the supplied interrupt vector and sets the value of the state parameter to either 1 or 0 depending on whether there is already an ISR attached to the vector. The HAL will only allow one ISR to be attached to each vector, so it is a good idea to use this function before using HAL_INTERRUPT_ATTACH().

HAL_INTERRUPT_ATTACH() attaches the ISR, data pointer and object pointer to the given vector. When an interrupt occurs on this vector the ISR is called using the C calling convention and the vector number and data pointer are passed to it as the first and second arguments respectively.

HAL_INTERRUPT_DETACH() detaches the ISR from the vector.

HAL_VSR_SET() replaces the VSR attached to the vector with the replacement supplied in vsr. The old VSR is returned in the location pointed to by pvsr. On some platforms, possibly only in certain configurations, the table of VSRs will be in read-only memory. If so then this macro should be left undefined.

HAL_VSR_GET() assigns a copy of the VSR to the location pointed to by pvsr.

HAL_VSR_SET_TO_ECOS_HANDLER() ensures that the VSR for a specific exception is pointing at the eCos exception VSR and not one for RedBoot or some other ROM monitor. The default when running under RedBoot is for exceptions to be handled by RedBoot and passed to GDB. This macro diverts the exception to eCos so that it may be handled by application code. The arguments are the VSR vector to be replaces, and a location in which to store the old VSR pointer, so that it may be replaced at a later point. On some platforms, possibly only in certain configurations, the table of VSRs will be in read-only memory. If so then this macro should be left undefined.

Interrupt controller management

HAL_INTERRUPT_MASK( vector )
HAL_INTERRUPT_UNMASK( vector )
HAL_INTERRUPT_ACKNOWLEDGE( vector )
HAL_INTERRUPT_CONFIGURE( vector, level, up )
HAL_INTERRUPT_SET_LEVEL( vector, level )

These macros exert control over any prioritized interrupt controller that is present. If no priority controller exists, then these macros should be empty.

Note: These macros may not be reentrant, so care should be taken to prevent them being called while interrupts are enabled. This means that they can be safely used in initialization code before interrupts are enabled, and in ISRs. In DSRs, ASRs and thread code, however, interrupts must be disabled before these macros are called. Here is an example for use in a DSR where the interrupt source is unmasked after data processing:
 ...
 HAL_DISABLE_INTERRUPTS(old);
 HAL_INTERRUPT_UNMASK(CYGNUM_HAL_INTERRUPT_ETH);
 HAL_RESTORE_INTERRUPTS(old);
 ...

HAL_INTERRUPT_MASK() causes the interrupt associated with the given vector to be blocked.

HAL_INTERRUPT_UNMASK() causes the interrupt associated with the given vector to be unblocked.

HAL_INTERRUPT_ACKNOWLEDGE() acknowledges the current interrupt from the given vector. This is usually executed from the ISR for this vector when it is prepared to allow further interrupts. Most interrupt controllers need some form of acknowledge action before the next interrupt is allowed through. Executing this macro may cause another interrupt to be delivered. Whether this interrupts the current code depends on the state of the CPU interrupt mask.

HAL_INTERRUPT_CONFIGURE() provides control over how an interrupt signal is detected. The arguments are:

vector: The interrupt vector to be configured.
level: Set to true if the interrupt is detected by level, and false if it is edge triggered.
up: If the interrupt is set to level detect, then if this is true it is detected by a high signal level, and if false by a low signal level. If the interrupt is set to edge triggered, then if this is true it is triggered by a rising edge and if false by a falling edge.

HAL_INTERRUPT_SET_LEVEL() provides control over the hardware priority of the interrupt. The arguments are:

vector: The interrupt whose level is to be set.
level: The priority level to which the interrupt is to set. In some architectures the masking of an interrupt is achieved by changing its priority level. Hence this function, HAL_INTERRUPT_MASK() and HAL_INTERRUPT_UNMASK() may interfere with each other.