TSS463 ATMEL Corporation, TSS463 Datasheet - Page 23

• Manufacturer Part Number: TSS463
• Description: VAN Data Link Controller with Serial Interface
• Manufacturer: ATMEL Corporation

Internal Operations
Digital Filtering
Transition Analyses
4102E–AUTO–12/04
Status bits give permanent information on the diagnosis performed, whatever the pro-
grammed operating mode. This is encoded over three bits: Sa, Sb and Sc.
•
Table 3. Status Bits: Sa and Sb
•
The only way to reset this status bit is through the RI signal or a general reset.
If several spurious pulses occur during one bit, the diagnosis for defective conductor
may be corrupted. To avoid such errors, digital filters are implemented.
Filtering operation is based on sampling of the comparator output signals. A transition is
taken into account only if it is observed over five samples (1/16
These analyses are continuously done on the effective edges on comparators after digi-
tal filtering.
•
•
Sa
Sa and Sb bits indicate the four possible states of the VAN bus.
Sc: As soon as one of the three inputs (RXD2, RXD1, RXD0) differs from the others
in the input comparison analysis performs by the diagnosis system, Sc is set.
Asynchronous diagnosis
The asynchronous diagnosis is done by comparing the number of edges on DATA
and DATA.
If four edges are detected on one input and no edges on the other during the same
period, the second input is considered faulty and the diagnosis mode will change to
one of the degraded modes.
Synchronous diagnosis
The synchronous diagnosis counts the number of edges on the data input
connected to the reception logic during one SDC period.
If there are less than four edges during one SDC period, the diagnosis mode will
change to the major error mode.
0
0
1
1
Sb
0
1
0
1
Status
Status
Status
Status
Mode
Mode
Mode
Mode
Fault
Fault
Fault
Fault
Communication
Nominal
No fault on VAN bus
Differential communication on DATA and DATA
Degraded on DATA
Fault on DATA
Communication on DATA
Degraded on DATA
Fault on DATA
Communication on DATA
Major error
Fault on DATA and DATA
No communication on DATA and DATA (attempt to communicate
alternatively on DATA then DATA every SDC period)
th
of timeslot).
TSS463B
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