— eCos Support for a Nios II Avalon Timer-based Watchdog Device
A Nios II hardware design can include an Avalon timer which acts as a
watchdog device. Once started it will automatically reset the
processor unless software updates the device at regular intervals. The
provides an eCos driver for this device, complementing the generic
CYGPKG_IO_WATCHDOG. The functionality
should be accesssed via the standard eCos watchdog functions.
The Avalon watchdog driver package should be loaded automatically when
creating an eCos configuration for a hardware design which includes a
suitable watchdog device, and it should never be necessary to load the
package explicitly. The package is inactive unless the generic
CYGPKG_IO_WATCHDOG is loaded.
Depending on the choice of eCos template it may be necessary to load
The package provides a configuration option
CYGIMP_WATCHDOG_HARDWARE. This can be used to
disable the use of the hardware watchdog and switch to a software
emulation provided by the generic watchdog package instead. This may
prove useful during debugging. The package also provides two
configuration options for manipulating the compiler flags used to
build the driver.
A hardware design requiring a watchdog should include an Avalon timer labelled “watchdog”. This timer should use the presets for a watchdog device: no writeable period, no readable snapshot, no start/stop control bits, no timeout pulse, system reset on timeout. The watchdog period can be set to any desired value, subject to the constraints of a 32-bit counter and the hardware's input clock. For example if the hardware runs at 100MHz then the watchdog period is limited to at most 42.9 seconds.
The hardware design HAL package should include definitions for
HAL_NIOS2_AVALON_TIMER_WATCHDOG_PERIOD. In addition
the ecos.db target entry should list
CYGPKG_DEVS_WATCHDOG_NIOS2_AVALON_TIMER as one of
the hardware packages.
|2018-06-19||eCosPro Non-Commercial Public License|