MC68336/376
REGISTER SUMMARY
MOTOROLA
USER’S MANUAL
Rev. 15 Oct 2000
D-87
D.10.5 Control Register 1
SAMP — Sampling Mode
The SAMP bit determines whether the TouCAN module will sample each received bit
one time or three times to determine its value.
0 = One sample, taken at the end of phase buffer segment 1, is used to determine
the value of the received bit.
1 = Three samples are used to determine the value of the received bit. The sam-
ples are taken at the normal sample point, and at the two preceding periods of
the S-clock.
LOOP — TouCAN Loop Back
The LOOP bit configures the TouCAN to perform internal loop back. The bit stream
output of the transmitter is fed back to the receiver. The receiver ignores the CANRX0
and CANRX1 pins. The CANTX0 and CANTX1 pins output a recessive state. In this
state, the TouCAN ignores the ACK bit to ensure proper reception of its own messag-
es.
0 = Internal loop back disabled.
1 = Internal loop back enabled.
TSYNC — Timer Synchronize Mode
The TSYNC bit enables the mechanism that resets the free-running timer each time a
message is received in message buffer 0. This feature provides the means to synchro-
nize multiple TouCAN stations with a special “SYNC” message (global network time).
0 = Timer synchronization disabled.
1 = Timer synchronization enabled.
NOTE
There can be a bit clock skew of four to five counts between different
TouCAN modules that are using this feature on the same network.
LBUF — Lowest Buffer Transmitted First
The LBUF bit defines the transmit-first scheme.
0 = Message buffer with lowest ID is transmitted first.
1 = Lowest numbered buffer is transmitted first.
PROPSEG[2:0] — Propagation Segment Time
PROPSEG defines the length of the propagation segment in the bit time. The valid pro-
grammed values are 0 to 7. The propagation segment time is calculated as follows:
CANCTRL1 — Control Register 1
$YFF087
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
CANCTRL0
SAMP LOOP
TSYN
C
LBUF
RSVD
PROPSEG[2:0]
RESET:
0
Propagation Segment Time
PROPSEG
1
+
()Time Quanta
=