
On-chip peripherals
ST7L34, ST7L35, ST7L38, ST7L39
Doc ID 11928 Rev 7
Figure 66.
LDIV read/write operations when LDUM = 1
LINSCI clock tolerance
LINSCI clock tolerance when unsynchronized
When LIN slaves are unsynchronized (meaning no characters have been transmitted for a
relatively long time), the maximum tolerated deviation of the LINSCI clock is
±15%.
If the deviation is within this range then the LIN synch break is detected properly when a
new reception occurs.
This is made possible by the fact that masters send 13 low bits for the LIN synch break,
which can be interpreted as 11 low bits (13 bits -15% = 11.05) by a ‘fast’ slave and then
considered as a LIN synch break. According to the LIN specification, a LIN synch break is
valid when its duration is greater than tSBRKTS = 10. This means that the LIN synch break
must last at least 11 low bits.
Note:
If the period desynchronization of the slave is +15% (slave too slow), the character ‘00h’
which represents a sequence of 9 low bits must not be interpreted as a break character (9
bits + 15% = 10.35). Consequently, a valid LIN synch break must last at least 11 low bits.
LINSCI clock tolerance when synchronized
When synchronization has been performed, following reception of a LIN synch break, the
LINSCI, in LIN mode, has the same clock deviation tolerance as in SCI mode, which is
explained below:
During reception, each bit is oversampled 16 times. The mean of the 8th, 9th and 10th
samples is considered as the bit value.
Consequently, the clock frequency should not vary more than 6/16 (37.5%) within one bit.
The sampling clock is resynchronized at each start bit, so that when receiving 10 bits (one
start bit, 1 data byte, 1 stop bit), the clock deviation should not exceed 3.75%.
RDRF = 1
Write LPR
Write LPFR
LDIV_NOM
FRAC(3:0)
MANT(7:0)
LIN sync field
measurement
Update
at end of
synch field
MANT(7:0)
FRAC(3:0)
LDIV_MEAS
MANT(7:0)
LDIV
FRAC(3:0)
Baud rate generation
Read LPR
Read LPFR