Echelon Series 6000 Chip databook - Manual (Page 62)

in the communications medium, or instability in the transmitting or receiving device’s input
clocks. The jitter tolerance windows are expressed as fractions of the bit period, T.
Table 18. Receiver Jitter Tolerance Windows
Next Data Edge (Nominal)
Next Clock Edge
(Nominal)
Line Code Violation to
Receive (Minimum)
0.500T 1.000T 1.46T
For the receiver to reliably terminate reception of a packet, the received line-code violation
period must have no transitions until the Neuron Chip detects the end of the packet. The
receiving Neuron Chip terminates a packet if no clock transitions are detected after the last
bit. Table 18 shows the minimum duration from the last clock edge to where the Neuron
Chip is guaranteed to recognize the line-code violation. Data transitions are allowed in this
period (and must fall within the data window).
For a Neuron Chip, the time from when an application software call is issued to send a 12-
byte message to when the packet is sent is approximately 175 µs for an 80 MHz system clock
(the time varies inversely with the system clock rate).
Special-Purpose Mode
In special situations, it is desirable for the Neuron Chip to provide the packet data in an
unencoded format and without a preamble. In this case, an intelligent transmitter accepts
the unencoded data and does its own formatting and preamble insertion. The intelligent
receiver then detects and strips off the preamble and formatting, and returns the decoded
data to the Neuron Chip.
Such an intelligent transceiver contains its own input and output data buffers and intelligent
control functions, and provides handshaking signals to properly pass the data back and forth
between the Neuron Chip and the transceiver. In addition, there are many features that can
be defined by and incorporated into a special-purpose transceiver:
• Ability to configure various parameters of the transceiver from the Neuron Chip
• Ability to report on various parameters of the transceiver to the Neuron Chip
• Multiple channel operation
• Multiple bit rate operation
• Use of forward error correction
• Media-specific modulation techniques requiring special message headers and framing
• Collision detection
While the special-purpose mode offers custom features, it is expected that most transceivers
will use the single-ended mode for most types of media. This is because single-ended mode
offers Differential Manchester encoding, which takes care of clock recovery, whereas special-
purpose mode does not have this feature. In addition, the special-purpose mode is a
PATENT NOTICE
The Special-Purpose Mode is protected by U.S. Patent No. 5,182,746 and foreign patents
based on this patent. No express or implied license is granted herein with respect to such
patents. If you are interested in obtaining a non-exclusive, royalty free license to these
patents, please call Echelon at +1 (408) 938 5200 and ask for Contracts Management.
50 Hardware Resources