ADLINK HSL-DO32-M-N/HSL-DO32-M-P - Manual (Page 39)

26 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.