TSS461 ATMEL Corporation, TSS461 Datasheet - Page 42

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

Messages
Types
42
TSS461E
There are 5 basic message types defined in the TSS461E. Two of them (transmit and receive
message types) correspond to the normal frame, and the rest correspond to the different ver-
sions of reply frames.
To transmit a normal data frame on the VAN bus, the user must program an identifier as a
Transmit Message. The TSS461E will then transmit this message on the bus until it has suc-
ceeded 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 dif-
fer 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 TSS461E
will set the message type to the after transmission state. When this message type is pro-
grammed, the TSS461E will listen on the bus for a deferred reply frame matching this identifier,
without transmitting the reply request.
After Transmission
Initial Setup
After Transmission
After Transmission
(Waiting for reply)
After Reception
Initial Setup
Initial Setup
(of reply)
RNW
0
0
RNW
RNW
Receive Message
0
0
1
1
1
RTR
1
1
Reply Request Message
Transmit Message
RTR
RTR
0
0
1
1
1
Unchanged
Don’t Care
CHTx
CHTx
CHTx
0
1
0
1
1
CHRx
0
1
4194C–AUTO–01/06
Unchanged
Don’t Care
CHRx
CHRx
0
0
1