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Program Interface Library
CEI-x20 Interrupt Support
CEI-100/CEI-200/CEI-
x20 User’s Manual
61
All of the CEI-x20 boards accept (and produce) ARINC 429 words in
engineering format; there is no need to call AR_REFORMAT. In fact, if
the CEI-x20 library function AR_REFORMAT is called, it performs no
operation; it returns the ARINC word unchanged.
ARINC Parity
The CEI-100/200/x20 hardware also handles the ARINC parity bit in a
special way. You don’t need to calculate parity for transmission. The
hardware automatically calculates parity and overwrites bit 32 (parity)
with the calculated parity. Use AR_SET_CONFIG to program the parity
to ODD or EVEN for each transmitter. This parity function can be
disabled using the routine AR_SET_RAW_MODE.
For received words, the CEI-100/200/x20 hardware calculates the parity.
If the parity is ODD, it puts a zero in bit 32. Otherwise, it puts a one there.
This is so that the user can easily check the parity bit for error. If the
channel is set for ODD parity (normal), then a non-zero bit 32 indicates a
parity error. This can be overridden using the routine,
AR_SET_RAW_MODE, which can be used to disable parity altogether.
CEI-x20 Interrupt Support
Functions are included in the CEI-x20 API to allow configuration of
hardware interrupt generation. The current API does not provide a user
application interrupt handler function. If your application uses hardware
interrupts, you have to supply an interrupt handler as needed by your
operating environment (operating system and host int controller).
To support receiver 'await data' mode, limited internal interrupt handling
capability was added to the CEI-x20 API for select boards and operating
systems (refer to AR_SET_PRELOAD_CONFIG documentation for
details). No user application interrupt handling capability is provided, and
calling CEI-x20 interrupt support routines when internal interrupt handling
is enabled should be avoided.
Receiver ‘Await Data’ Mode
A special receive mode ('await data' mode) is provided that allows a user
program to wait until data is received on a particular channel. This mode
is currently only supported by the CEI-820 under Red Hat Linux
Enterprise 4.0 (kernel versions 2.6.17.13, 2.6.18, 2.6.20.14, 2.6.22.2, and
2.6.22.19 only).
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