TSS461 ATMEL Corporation, TSS461 Datasheet - Page 19

• Manufacturer Part Number: TSS461
• Description: VAN Data Link Controller
• Manufacturer: ATMEL Corporation

Diagnosis
System
Diagnosis States
Figure 16. Diagnosis States
4194C–AUTO–01/06
DEGRATED
DATA
- Failure during the frame.
- Default of transitions on the valid input between 2 consecutive SDC rising edges.
- Protocol fault
- In specified selection mode, every RI pulse when an EOF is detected or through an active SDC.
- In automatic selection mode and SDC active, no failure sampled by 2 consecutive SDC rising edges.
- General reset
The purpose of the diagnosis system is to detect any short or open circuits on either the DATA
or DATA lines and to permit, if it is possible, to carry the communications on the non-defective
line.
The diagnosis system is based on the assumption that three separate line receivers are con-
nected to the VAN bus (see Figure 3):
•
•
The diagnosis system analyzes and compares the data sent over both VAN lines. So, the diag-
nosis system executes a digital filtering and transition analyses. In order to perform its
investigation, three internal signals are generated, RI (Return to Idle), SDC (Synchronous Diag-
nosis Clock) and TIP (Transmission In Progress).
One of four operating modes can be chosen to manage the results of the diagnosis system.
If the diagnosis system finds a failure on either of the VAN bus signals, it changes from nominal
to degraded mode, and connects the line receiver not coupled to the failing signal to the recep-
tion logic.
When the diagnosis system finds that the failing signal is working again, it returns to nominal
mode and re-connects the differential line receiver to the reception logic.
A major error occurs when both the VAN bus signals fail.
Status bits give permanent information on the diagnosis performed, whatever the programmed
operating mode. This is encoded over three bits: Sa, Sb and Sc. Sa and Sb bits indicate the four
possible states of the VAN bus.
One of the line receivers is connected in differential mode, sensing both DATA and DATA
signals, and is connected to the RxD0 input.
The other two line receivers are operating in single wire mode and are sensing only one of
the two VAN bus signals:
–
–
The line receiver sensing DATA is connected to RxD1
The line receiver sensing DATA is connected to RxD2
NONIMAL
MAJOR
ERROR
DEGRATED
DATA
TSS461E
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