Bit Timing Unit - Infineon Technologies TC1728 User Manual

20.3.5.1 Bit Timing Unit

According to the ISO 11898 standard, a CAN bit time is subdivided into different
segments (Figure
t
magnitude of is adjusted by Node x Bit Timing Register bit fields NBTRx.BRP and
q
NBTRx.DIV8, both controlling the baud rate prescaler (register NBTRx is described on
Page 20-85). The baud rate prescaler is driven by the module timer clock
(generation and control of
Figure 20-9 CAN Bus Bit Timing Standard
The Synchronization Segment (T
transmitter and receiver time base. The Synchronization Segment length is always
t
one . The Propagation Time Segment (T
q
propagation delay in the transmitter output driver on the CAN bus line and in the
transceiver circuit. For a working collision detection mechanism, T
the sum of all propagation delay quantities rounded up to a multiple of
buffer segments 1 and 2 (T
compensate for a mismatch between transmitter and receiver clock phases detected in
the synchronization segment.
The maximum number of time quanta allowed for re-synchronization is defined by bit
field NBTRx.SJW. The Propagation Time Segment and the Phase Buffer Segment 1 are
combined to parameter T
of 3 time quanta is demanded by the ISO standard. Parameter T
the value of NBTRx.TSEG2, covers the Phase Buffer Segment 2. A minimum of 2 time
quanta is demanded by the ISO standard. According to ISO standard, a CAN bit time,
calculated as the sum of T
User's Manual
MultiCAN, V2.24
20-9). Each segment consists of multiples of a time quantum
f
is described on
CAN
T
Seg1
T T
Sync Prop
Sync.
Seg
1 Time Quantum (
Sync
, T ) before and after the signal sample point are used to
b1 b2
, which is defined by the value NBTRx.TSEG1. A minimum
Seg1
, T and T
Sync Seg1
Controller Area Network Controller (MultiCAN)
Page 20-115).
1 Bit Time
T
T T
b1
t
)
q
Sample Point
) allows a phase synchronization between
) takes into account the physical
Prop
, must not fall below 8 time quanta.
Seg2
20-22
Seg2
b2
Transmit Point
MCT06266
must be two times
Prop
t
q
, which is defined by
Seg2
TC1728
t
. The
q
f
CAN
. The phase
V1.0, 2011-12