1996 Jun 19
18
Philips Semiconductors
Preliminary specification
CAN Serial Linked I/O device (SLIO) with
digital and analog port functions
P82C150
7.3.5
B
IT
T
IMING
The Nominal Bit Time of the P82C150 is subdivided into 10
Time Quanta. The Synchronization Time Segment
(SYNC_SEG) and the Propagation Time Segment
(PROP_SEG) are each one Time Quantum long. The
Phase Buffer Segment 1 (PHASE_SEG1) and the Phase
Buffer Segment 2 (PHASE_SEG2) are each four Time
Quanta long. The Resynchronization Jump Width (SJW) is
four Time Quanta long.
The sample point is located at the end of the Phase Buffer
Segment 1. The Nominal Bit Time is internally adjusted to
that bit timing which is provided by the crystal driven host
(calibration message).
The usable bus length at a given bit rate is reduced in
comparison to other CAN controllers with programmable
bit timing because the Propagation Time Segment is fixed
to
1
10
length of the Nominal Bit Time. The bit segmentation
of the crystal driven host should be programmed like the
fixed bit segmentation of the P82C150, e.g. one bit time
segment is
1
10
length of the Nominal Bit Time (refer also
to Table 15 for bit time programming).
Table 11
Bit time subdivision
1 BIT TIME
BT1
BT2
BT3
BT4
BT5
BT6
BT7
BT8
BT9
BT10
SYNC_SEG
PROP_SEG
PHASE_SEG1
PHASE_SEG2
7.3.6
CAN-B
US
T
RANSCEIVER
The transceiver of the P82C150 consists of the
configurable input comparator and of complementary
open-drain driver outputs. The reference voltage REF is
an additional output.
7.3.6.1
CAN-bus input comparator (RX0, RX1)
The input comparator monitors the transient voltage on
RX1 and RX0.
The result of the input comparator is logic 1 if the voltage
levels of the CAN-bus lines are regarded as recessive, and
logic 0 if they are regarded as dominant.
The recessive state and the dominant state are not
equivalent and may not be mixed-up.
The input comparator is configurable depending on the
four CAN-bus modes (see Table 10), supporting
battery-powered applications (Sleep Mode) and tolerance
against bus wiring failures.
7.3.6.2
CAN-bus output drivers (TX0, TX1)
The output driver function is shown in Table 12. The output
driver TX1 is disabled in bus mode 2 to tolerate a
short-circuit between the CAN-bus lines in a two-wire
differential CAN physical layer.
Table 12
CAN-bus driver output function
CAN OUTPUT
RECESSIVE
DOMINANT
RESET STATE, BUS-OFF AND
SLEEP MODE (MODE 3)
MODES 0 AND 1
MODE 2
TX0
TX1
floating
floating
LOW
HIGH
LOW
floating
floating
floating