Interrupts
Am186™CC/CH/CU Microcontrollers User’s Manual
7-13
7.5.5
Maskable Interrupts
7.5.5.1
Maskable Interrupt Cycle
When the interrupt controller receives a request, it does the following:
1. Sets the appropriate channel bit in the Interrupt Request (REQST) register to indicate
a pending interrupt. If the request is from the on-board timers or general-purpose DMA,
it also sets the appropriate bit in the Interrupt Status (INTSTS) register to indicate a
pending interrupt. If the request is for a Channel 14 interrupt, it also sets a bit in the
Shared Request (SHREQ) register to indicate a pending interrupt.
2. Verifies the request by checking that the interrupt is enabled. An interrupt is enabled
when the associated MSK bit in the IMASK register is set. An interrupt request coming
in through the shared request channel, Channel 14, must also have the associated MSK
bit in the SHMASK register set. If the associated MSK bit is not set, the interrupt is not
recognized.
3. Verifies that the requesting interrupt’s priority, set in the PRI field of the CHxCON register,
is equal to or greater than the priority set in the PRIMASK register. If the interrupt source
has not been programmed to equal or greater priority than the PRIMASK, the interrupt
is not recognized.
4. Compares the programmable priority of the requesting interrupt with that of any interrupts
currently in service. If the interrupt source is not of equal or greater priority than the
highest priority interrupt in service, the interrupt is not recognized.
5. If the interrupt is recognized, the controller generates an interrupt request to the
execution unit.
6. If the IF flag in the FLAGS register is set, the execution unit recognizes the request.
Otherwise, the request remains pending until interrupts are enabled or the interrupting
condition is cleared.
7. Passes the interrupt type (also called interrupt number) to the bus interface so the
processor can fetch the associated vector from the interrupt vector table. The interrupt
type provides an index into the interrupt vector table. The actual interrupt vector, the
address of the interrupt service routine, is found in the table at the address indicated by
the interrupt type times 4.
8. Sets the associated CH bit for the interrupt channel in the INSERV register to indicate
that an interrupt on that channel is currently being serviced by software.
9. The controller clears the CH bit for the channel when an EOI instruction is executed with
either of two conditions: a specific EOI that specifies this channel or a non-specific EOI
when this channel is the highest priority interrupt whose CH bit is set.
3. The type and overall priority for the INT1–INT7 pins in this table assume that these pins are being serviced by
a dedicated channel; that is, they are not being serviced by channel 14. When the INT1–INT7 pins are being ser-
viced by Channel 14, they share type 1Eh, overall priority 15, as indicated by the last row in Table 7-3.
4. PWD is generated on the Low-to-High transition of the PWD input; the second PWD is generated on the High-
to-Low transition.
5. See the SHREQ register description in the Am186™CC/CH/CU Microcontrollers Register Set Manual, order
#21916, for information on the shared Channel 14.
Содержание Am186 CC
Страница 1: ...Am186 CC CH CU Microcontrollers User s Manual Order 21914B...
Страница 4: ...iv Am186 CC CH CU Microcontrollers User s Manual...
Страница 18: ...Table of Contents xviii Am186 CC CH CU Microcontrollers User s Manual...
Страница 24: ...Introduction xxiv Am186 CC CH CU Microcontrollers User s Manual...
Страница 39: ...Architectural Overview Am186 CC CH CU Microcontrollers User s Manual 1 15 Figure 1 6 32 Channel Linecard CH CC...
Страница 40: ...Architectural Overview 1 16 Am186 CC CH CU Microcontrollers User s Manual...
Страница 86: ...System Overview 3 36 Am186 CC CH CU Microcontrollers User s Manual...
Страница 92: ...Emulator Support 4 6 Am186 CC CH CU Microcontrollers User s Manual...
Страница 112: ...DRAM Controller 6 8 Am186 CC CH CU Microcontrollers User s Manual...
Страница 134: ...Interrupts 7 22 Am186 CC CH CU Microcontrollers User s Manual...
Страница 186: ...Programmable I O Signals 9 8 Am186 CC CH CU Microcontrollers User s Manual...
Страница 200: ...Watchdog Timer 11 6 Am186 CC CH CU Microcontrollers User s Manual...
Страница 232: ...Asynchronous Serial Ports UARTs 13 24 Am186 CC CH CU Microcontrollers User s Manual...
Страница 242: ...Synchronous Serial Port SSI 14 10 Am186 CC CH CU Microcontrollers User s Manual...
Страница 264: ...High Level Data Link Control HDLC 15 22 Am186 CC CH CU Microcontrollers User s Manual...
Страница 332: ...Universal Serial Bus USB 18 34 Am186 CC CH CU Microcontrollers User s Manual...
Страница 348: ...Register Summary A 16 Am186 CC CH CU Microcontrollers User s Manual...
Страница 376: ...Index Index 18 Am186 CC CH CU Microcontrollers User s Manual...