User’s Manual
C166S V1 SubSystem
Central Processing Unit
User’s Manual
3-19
V 1.6, 2001-08
3.4.1
Interrupt System Structure
The C166S provides up to 112 separate interrupt nodes that may be assigned to 128
arbitration priority levels with 16 interrupt priority groups and 4/8 priorities inside each
group. In order to support modular and consistent software design techniques, most
sources of an interrupt or PEC request are supplied with a separate interrupt control
register and interrupt vector. The control register contains an interrupt request flag,
Interrupt Enable (IE) bit, and interrupt priority of the associated source. Each source
request is activated by one specific event, depending on the selected operating mode of
the respective device. In some cases, the multi-source interrupt nodes are incorporated
for efficient use of system resources. These nodes can be activated by several source
requests.
The C166S provides a vectored interrupt system. This system reserves specific vector
locations in the memory space for the reset, trap, and interrupt service functions.
Whenever a request occurs, the CPU branches to the location that is associated with the
respective interrupt source. The reserved vector locations build a jump table in the
C166S’s address space.
The arbitration winner is sent to the CPU together with its priority level and action
request. The CPU triggers the corresponding action, which depends on the required
functionality (normal interrupt, PEC etc.) of the arbitration winner.
An action request will be accepted by the CPU if the requesting source has a higher
priority than the current CPU priority level, and if interrupts are globally enabled. If the
requesting source has a lower (or equal) interrupt level priority, then the requested
interrupt stays pending.
3.4.2
Interrupt Arbitration
The C166S interrupt arbitration system can handle interrupt requests from up to 112
sources. Interrupt requests may be triggered either by the C166S peripherals or by
external inputs. The “End of PEC” interrupt for supporting enhanced PEC functionality is
connected internally to one of the interrupt request lines.
The arbitration process starts by an enabled interrupt request and stays active for as
long as interrupt request is pending. If nothing is pending then the arbitration logic
switches to the idle state to save power.
Each interrupt request line is controlled by its interrupt control register xxIC (here and
below, ’xx’ stands for the mnemonic of the respective interrupt source). An interrupt
request event sets the interrupt request flag to 1 in the corresponding interrupt control
register (bit xxIC.xxIR). The interrupt request can also be triggered by the software if the
program sets the respective interrupt request bit. This feature is used by operating
systems.
If the request bit has been set and this interrupt request is enabled by the IE bit of the
same control register (bit xxIC.xxIE), then an arbitration cycle starts on the next clock
Содержание C166S V1 SubSystem
Страница 10: ...User s Manual C166S V1 SubSystem User s Manual I 6 V 1 6 2001 08...
Страница 16: ...User s Manual C166S V1 SubSystem Introduction User s Manual 1 6 V 1 6 2001 08...
Страница 126: ...User s Manual C166S V1 SubSystem Central Processing Unit User s Manual 3 96 V 1 6 2001 08...
Страница 178: ...User s Manual C166S V1 SubSystem Memory Organization User s Manual 4 52 V 1 6 2001 08...
Страница 206: ...User s Manual C166S V1 SubSystem Instruction Set User s Manual 5 28 V 1 6 2001 08...
Страница 306: ...User s Manual C166S V1 SubSystem Detailed Instruction Set User s Manual 6 100 V 1 6 2001 08...
Страница 362: ...User s Manual C166S V1 SubSystem The External Bus Interface User s Manual 8 40 V 1 6 2001 08...
Страница 452: ...User s Manual C166S V1 SubSystem General Purpose Timer Unit User s Manual 12 44 V 1 6 2001 08...
Страница 454: ...User s Manual C166S V1 SubSystem Instruction Index User s Manual 13 2 V 1 6 2001 08...
Страница 459: ......