Am186™CC/CH/CU Microcontrollers User’s Manual
11-1
CHAPTER
11
WATCHDOG TIMER
11.1
OVERVIEW
The Am186CC/CH/CU microcontrollers provide a full-featured watchdog timer that can
generate nonmaskable interrupts (NMIs), internal resets, and system resets when the time-
out value is reached. The time-out value is programmable and ranges from 2
10
to 2
26
processor clocks. Throughout this chapter, an
external reset refers to a reset of the
microcontroller as initiated by the RES signal, which resets the CPU and the internal
peripherals.
Internal reset refers to a reset initiated by the watchdog timer. System reset
refers to a reset of the external peripherals connected to the controller as initiated by the
RESOUT signal, which is pulled Low during an external reset and can be pulled Low during
an internal reset.
The watchdog timer provides a method to regain control when a system has failed due to
a software error or to the failure of an external device to respond in the expected way.
Software errors can sometimes be resolved by recapturing control of the execution
sequence through a watchdog-timer-generated NMI. When an external device fails to
respond, or responds incorrectly, it may be necessary to reset the controller or the entire
system, including external devices. The watchdog timer provides the flexibility to support
both NMI and reset generation. The watchdog timer is enabled at reset.
11.2
BLOCK DIAGRAM
Figure 11-1 shows a block diagram of the watchdog timer.
Figure 11-1
Watchdog Timer Block Diagram
Watchdog Timer
(external) RES
RESOUT
Execution
Unit
(external) NMI
Internal NMI
Internal RES
Internal
RD
WR
DATA
Peripheral
Reset Control
Counter
Key Detect
Devices
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...