TSS461C datasheet(42/57 Pages) ATMEL

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TSS461C

4193G–AUTO–12/04

Messages Types

There are 5 basic message types defined in the TSS461C. Two of them (transmit and

receive message types) correspond to the normal frame, and the rest correspond to the

different versions of reply frames.

To transmit a normal data frame on the VAN bus, the user must program an identifier as

a Transmit Message. The TSS461C will then transmit this message on the bus until it

has succeeded or the retry count is exceeded.

The opposite of the transmit message type is the Receive Message type. This message

type will not generate any frames on the bus. Instead, it will listen to the bus until a

frame passes that matches its identifier, with the mask taken into account, and then

receive the data in that frame.

The data received will be stored in the message buffer and the length of the message

received is stored in the first byte of the message buffer.

The actual identifier received is stored in the identifier register itself. This identifier may

differ from the identifier specified in the register due to the effect of the mask register.

Normally, this should not interfere with the next identifier comparison since the bits that

may differ are masked via the mask register.

The Reply Request Message type is a demand to transmit on the VAN bus a reply

request. When this message type is programmed, three things can happen.

First, no other modules on the bus responded with an in-frame reply, in this case the

TSS461C will set the message type to the after transmission state. When this message

type is programmed, the TSS461C will listen on the bus for a deferred reply frame

matching this identifier, without transmitting the reply request.

Transmit Message

RNW

RTR

CHTx

CHRx

Initial Setup

Don’t Care

After Transmission

Unchanged

Receive Message

RNW

RTR

CHTx

CHRx

Initial Setup

Don’t Care

After Transmission

Unchanged

Reply Request Message

RNW

RTR

CHTx

CHRx

Initial Setup

After Transmission

(Waiting for reply)

After Reception

(of reply)

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