
64 CME34BT cpuModule
BDM-610000088 Rev A
Watchdog Timer Control
The cpuModule includes a Watchdog Timer, which provides protection against programs “hanging”, or
getting stuck in an execution loop where they cannot respond correctly. The watchdog timer consists of a
counter, a reset generator, and an interrupt generator. When the counter reaches the interrupt time-out, it can
generate an interrupt. When the counter reaches the reset time-out, the system is reset. The counter is
“refreshed,” or set back to zero by reading from a specific register. The watchdog can also be put into an
“inactive” state, in which no resets or interrupts are generated.
The ability to generate an interrupt allows the application to gracefully recover from a bad state. For
example, consider a system that has a reset time-out of 2 seconds, interrupt time-out of 1 second, and the
watchdog timer is refreshed every 0.5 seconds. If something goes wrong, an interrupt is generated. The
Interrupt service routine then attempts to restart the application software. If it is successful, the application
is restarted in much less time than a full reboot would require. If it is not successful, the system is rebooted.
Due to system latency, it is recommended that the Watchdog be refreshed at about half of the reset time-out
period, or half of the interrupt time-out period, whichever is applicable.
Register Description
The Advanced Watchdog Timer has a Setup Register and a Runtime Register. The Setup Register is set by
the BIOS, and can be adjusted by entering the BIOS Setup Utility, and going to “Advanced”, “RTD
Advanced Options”, “RTD Miscellaneous Feature Control”. The Setup Register may also be read by the
driver to determine if the Watchdog is enabled, and the interrupt and base address that it is using.
Reading the Runtime Register also refreshes the watchdog timer.
Note
Enabling the watchdog timer in the BIOS does not actually arm it. The watchdog timer
can be armed by accessing I/O address E85h, as explained below.
Table 39 Advanced Watchdog Setup Register E8Bh
D7 D6 D5 D4
D3
D2
D1
D0
Reserved
WDT_IRQ
Select Interrupt for
WDT
000 = Disabled
001 = IRQ5
010 = Reserved
011 = IRQ10
100 = IRQ11
101 = Reserved
110 = IRQ3
111 = IRQ6
Reg_Enable
0 = Watchdog timer is disabled and
Runtime Register will not
appear in I/O map
1 = Watchdog Timer is enabled.
Runtime Register will appear in
I/O map
Table 40 Advanced Watchdog Runtime Register E85h
D7
D6
D5 D4
D3
D2
D1
D0
WDT_Active
0 = Watchdog
timer is
disabled.
1 = Watchdog is
armed and
can generate
resets and
interrupts.
WDT_IRQ_En
a
0 = Watchdog
interrupt is
disabled.
1 = Watchdog
interrupt is
enabled.
Reserved
WDT_IRQ_Ti
me
Select Interrupt
time for
WDT
00 = 0.25s
01 = 0.50s
10 = 0.75s
11 = 1.00s
WDT_RST_Ti
me
Select Reset
time for
WDT
00 = 2.00s
01 = 0.50s
10 = 0.75s
11 = 1.00s
Содержание cpuModules CME34BT
Страница 3: ... Accessing the Analog World www rtd com ISO9001 and AS9100 CME34BT cpuModules ...
Страница 34: ...26 CME34BT cpuModule BDM 610000088 Rev A ...
Страница 82: ...74 CME34BT cpuModule BDM 610000088 Rev A ...
Страница 88: ...80 CME34BT cpuModule BDM 610000088 Rev A Figure 12 CME34BTQ1910 Heatsink Edge near PCIe 104 ...
Страница 90: ...82 CME34BT cpuModule BDM 610000088 Rev A ...
Страница 105: ...BDM 610000088 Rev A Appendix C IDAN Dimensions and Pinout 97 ...
Страница 106: ...98 CME34BT cpuModule BDM 610000088 Rev A ...
Страница 108: ...100 CME34BT cpuModule BDM 610000089 Rev A ...
Страница 110: ...102 CME34BT cpuModule BDM 610000088 Rev A ...