C
OMPACT
CHAMP-AV IV U
SER
’
S
M
ANUAL
C
URTISS
-W
RIGHT
C
ONTROLS
E
MBEDDED
C
OMPUTING
1-14
814256 V
ERSION
2 F
EBRUARY
2006
Semaphore
Registers
There are sixteen 16-bit semaphore registers in the cOBIC. Any of the five processors may
clear the semaphore by writing 0x0000. Any of the five processors may claim the semaphore
by writing a non-zero value. However, the write will be ignored unless the semaphore value
is 0x0000 prior to the write. Thus, once a processor has written a non-zero value, no other
writes are allowed except a write of 0x0000. This functionality ensures that only one device
will own the semaphore at a time and that any device is able to clear the semaphore.
This scheme is backwards compatible with earlier software which writes a zero to bit 7 to
clear the register and cannot write to the register unless bit 7 of the register is a zero, and
the present write has bit 7 = 1.
These semaphore registers are typically used to coordinate the sharing of hardware
resources between multiple tasks. The hardware solution provides a faster alternative to
traditional software/memory techniques and avoids the use of shared memory and PCI
buses to access the semaphores.
Avionics Style
Watchdog Timer
The Compact CHAMP-AV IV provides five watchdog timers, one for each processor. Each
watchdog timer is a presettable up counter with a resolution of approximately 970 ns. Time-
out periods from 1 µs to 16 seconds can be programmed. Initialization software can select
whether a watchdog exception event causes an interrupt, a local processor reset, or a card
reset. The watchdog can be locked so that once enabled to cause a reset, the watchdog
cannot be disabled.
The watchdog timer can be used in two ways. As a standard watchdog timer, a single time
period is programmed which defines a maximum interval between writes to the watchdog
register. For increased system integrity, the watchdog can optionally be configured to
operate in “Avionics” mode whereby a minimum interval between writes to the watchdog
register is also enforced. In other words, writing to the watchdog register too soon or too
late causes an exception event. If a fault occurs the timer is stopped.
The following resources are provided for each Watchdog Timer:
• 24-bit Minimum timer
• 24-bit Maximum timer
• Watchdog Enable bit
• Watchdog "Kick" register
Note
Register information is provided for reference only. Use the BSL functions to manipulate the
semaphore registers.
T
ABLE
1.4:
Semaphore Register Format
15
14
13
12
11
10
9
8
Semaphore
owned tag
Semaphore
owned tag
Semaphore
owned tag
Semaphore
owned tag
Semaphore
owned tag
Semaphore
owned tag
Semaphore
owned tag
Semaphore
owned tag
7
6
5
4
3
2
1
0
Semaphore
owned tag
Semaphore
owned tag
Semaphore
owned tag
Semaphore
owned tag
Semaphore
owned tag
Semaphore
owned tag
Semaphore
owned tag
Semaphore
owned tag
Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com
