TSS461C
42
Rev. D (22 Feb 01)
MR[3:0]=1 indicates 1 retry, hence 2 transmission attempts will be performed (see Table 4. ). The number of retries
performed, as well as the current channel number associated, can be read in the Transmission Status Register (0x05).
The Last Error Status Register (0x07) informs about the trouble encounted:
Failure cases: - Code viol (CV error bit)
- Acknoledge error (ACKE error bit)
- CRC error (FCSE error bit)
It should be noticed that contention is considered as normal CSMA/CD protocol and, therefore, is not taken into
account in failure cases. So, an
’
infinite
’
number of attempts can be performed if bus contention occurs
continuously.
There is only one retries counter for all channels. When the user writes the Max_Retries value, all channels start their
transmission with this parameter.
13.2. Rearbitrate
The purpose of rearbitrate feature is to postpone a channel already in transmission in order to autorize an higher priority
(see section 12.) message to be transmit.
13.2.1. Typical example
Max_retries = 1 (2 transmissions attempts).
If Ch 8 is in a the retry loop and the user wants to transmit the Ch 5 without waiting the end of the loop, the user
can use the rearbitrate command.
Then, the TSS461C will wait the end of the current transmission, reload the retries counter and enable the Ch
5 to transmit.
At the end of this transmission Ch5, either when the attempt is successful or either when the exceeded retry count
is reached, the retries counter is reloaded and the transmission is activated for the Ch 8 again.
F
X
E
R
EOF+IFS
(
Delay
Viol
S
X
(
(
*
(
E
(
stand-by
F
X
S
X
(
Delay
Viol
S
E
a
Delay
Viol
EOF+IFS:
8 + 4 Timeslots
Delay Viol:
12 Timeslots
* (not seen by application means no IT generation)
Figure 26. Rearbitrate Example