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TSS461C
38
Rev. D (22 Feb 01)
11. 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.
Transmit Message
RNW
RTR
Transmitted
Received
Initial
setup
0
0
0
Dont care
After transmission
0
0
1
Unchanged
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.
Receive Message
RNW
RTR
Transmitted
Received
Initial
setup
0
1
Dont care
0
After transmission
0
1
Unchanged
1
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.
Reply Request Message
RNW
RTR
Transmitted
Received
Initial
setup
1
1
0
0
After
transmission
(Waiting
for reply)
1
1
1
0
After
reception
(of reply)
1
1
1
1
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.
In the first case no other modules on the bus responded with an in-frame reply, and 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.
The second case is that another module on the bus replies with an in-frame reply. In this case the message type will
pass immediatly into the after reception state, without passing the after transmission state.