7 communication error handling, Communication error handling – ADLINK HSL-AI16AO2-M-VV/-AV User Manual
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Introducing HSL
1.4.7 Communication error handling
The HSL communication protocol is designed to eliminate any
error, there may be some chances of communication errors such
as light striking, sudden off-line, etc. In an HSL system, the master
holds an accumulated slave-no-response count for every indi-
vidual slave I/O module. The count value is updated for each slave
module in every polling cycle.
X
If communication with certain slave I/O module is success-
ful, the no-response count value for this slave is set to 0.
X
If the communication failed, the no-response count value
increases by 1.
X
When the count is larger than or equal to 3, a binary flag
indexing communication error is set to True.
X
The maximum value of no-response count is 7. The value is
retained even if the error continues to occur.
The no-response count value and the communication error flag
status may be obtained by software function call. These error han-
dling data are also returned every time the user wants to set or get
the I/O values.
In addition, the HSL, through a software communication error-han-
dling driver, supports a self-diagnosis function that detects off-line
or out-of-communication slave modules. In a programmed period
of time (default 20 ms), the master sends an IRQ to trigger the
driver to check the slave’s no-response count value. If the count
value is 7, the driver informs the system that the slave module is
off-line.