TSS461C datasheet(19/57 Pages) ATMEL

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TSS461C

4193G–AUTO–12/04

Diagnosis System

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

connected to the VAN bus (see Figure 3):

•

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

The diagnosis system analyzes and compares the data sent over both VAN lines. So,

the diagnosis system executes a digital filtering and transition analyses. In order to per-

form its investigation, three internal signals are generated, RI (Return to Idle), SDC

(Synchronous Diagnosis Clock) and TIP (Transmission In Progress).

One of four operating modes can be chosen to manage the results of the diagnosis

system.

Diagnosis States

If the diagnosis system finds a failure on any of the VAN bus signals, it changes from

nominal to degraded mode, and connects the line receiver not coupled to the failing sig-

nal to the reception 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.

Figure 15. Diagnosis States

Nominal

Major

Error

Degraded

Data

Degraded

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.

TSS461C Datasheet(PDF) 19 Page - ATMEL Corporation

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