Figure 815. No Response - STMicroelectronics SPC572L series Reference Manual

RM0400
Header
Response timeout mechanism
•
Master mode
–
–
–
–
•
Slave mode
–
–
Response Time-out
OC2
T
Response_Max
OC2 is loaded with Nominal_time_out-Correction_factor at the end of the stop bit
of the Identifier field (where nominal_time_out = 1.4 × ((DFL + 2) × 10 bit time)).
The change with respect to earlier implementation is that this loading takes place
at the end of the ID field (and not at the beginning of the data field). Moreover, the
correct value, which depends on DFL, is loaded immediately. No further OC2
update is required.
In case of no response at all within this time (in other words, start of data is not
received), timeout takes place when the counter reaches the OC2 value (no
change compared to earlier implementation).
In case of an incomplete response, timeout also occurs when the counter reaches
the OC2 value (no change compared to earlier implementation).
Case 1: The received identifier is managed by a filter. The implementation can be
similar to the master mode, because the DFL value is loaded by hardware. Thus,
OC2 can be loaded with Nominal_time_out-Correction_factor at the end of the
stop bit of the Identifier field (where nominal_time_out = 1.4 × ((DFL + 2) × 10 bit
time)).
Case 2: The received identifier is not managed by a filter. As the DFL value needs
to be updated by software after the identifier field has been received, the previous
strategy cannot be used as the DFL value is not yet available. The earlier
implementation loaded the maximum value = 1.4 × (9 × 10 bit time) and then
updated it according to DFL after the first data byte reception. This was not
acceptable if no data byte was received at all, as timeout expired too late. The
proposed implementation is the following:
– At the end of the ID, OC2 is loaded with 36 (maximum possible response
space) + LINFlexD_LINTCSR[CNT]
– At the end of the first_data_byte it is reloaded again according to DFL
– Before reloading, LINFlexD checks the count_val. If count value is higher
than the value to be reloaded, timeout takes place immediately and no
reloading occurs.
DocID027809 Rev 4

Figure 815. No response

ERR
Header
LINFlexD
D1
D2 CRC
1423/2058
1506