P82C150AFT Philips Semiconductors, P82C150AFT Datasheet - Page 20

• Manufacturer Part Number: P82C150AFT
• Description: CAN Serial Linked I/O device SLIO with digital and analog port functions
• Manufacturer: Philips Semiconductors

Philips Semiconductors
7.4
7.4.1
Most of the P82C150 identifier bits are fixed. Four bits are
programmable via port pins P3 to P0. All output drivers are
disabled at reset, also P3 to P0. Thus the outputs are
floating unless the input level is defined by external
components to define identifier bits. They are latched at
the end of reset, and P3 to P0 can be used as port pins.
It is not allowed, according to the CAN protocol
specification, that multiple bus nodes transmit the same
identifier bit combination. Therefore a P82C150 must have
one of the 16 possible identifier bit combinations, one that
is not yet occupied.
7.4.2
RST = HIGH disables all output drivers P16 to P0, TX0
and TX1. All I/O Registers are automatically cleared and
set to logic 0. The bit time is set greater than 50 s.
If a particular clock period is necessary, e.g. for a
dedicated DPM output frequency, this can be achieved by
feeding an external clock signal into P0. RST and TEST
must be permanently HIGH for this special mode. A reset
is then performed as usual (RST = HIGH; TEST = LOW).
Table 14 Situation after RESET
7.4.3
The P82C150 must receive at least three messages to
calibrate its bit time after reset or change of bus mode.
The first message is used to detect the bit time length
(rough calibration) between two consecutive falling edges
at the output of the CAN input comparator. Therefore the
bit stream should contain a sequence of ‘1010’.
1996 Jun 19
RSTD = 1
EW = 1
BM1 = 0
BM0 = 0
CAN Serial Linked I/O device (SLIO) with
digital and analog port functions
Initialization
STATUS BITS
I
R
B
DENTIFIER PROGRAMMING
IT TIME CALIBRATION
ESET FUNCTION
ID.8 equals P3
ID.5 equals P2
ID.4 equals P1
ID.3 equals P0
IDENTIFIER BITS
20
After rough calibration the P82C150 can receive any valid
CAN message correctly and executes respective
commands without giving an acknowledge. With another
valid CAN message and additionally with one valid
calibration message the P82C150 is fully calibrated and
sends its ‘sign-on’ message. As long as the P82C150 is
fully calibrated the P82C150 acts as an active CAN node.
The P82C150 treats any CAN message (including the
calibration message) as a valid message, when these
messages are terminated by an error passive frame
because of a missing acknowledge. This situation may
occur whenever a host node works together with
P82C150’s and the host node doesn’t receive an
acknowledge as long as the P82C150’s are not fully
calibrated.
7.4.3.1
This special Data Frame is transmitted once by the
P82C150 after entering the calibrated state. It indicates to
the host node that the P82C150 is ready for transmission.
The sign-on message returns the contents of the Data
Input Register, and can be recognized by the host mode by
checking the RSTD status bit:
Note that in the sign-on message the EW bit is logic 1.
Nevertheless the P82C150 status with the error counters
are set to logic 0.
Sign-on message RSTD = 1
Other Data Frames RSTD = 0
Sign-on message
Preliminary specification
P82C150