Teledyne LeCroy Line Code and Symbolic Decoders - Manual (Page 7)

Instruction Manual
922663 Rev A 5
Manchester/NRZ Decoder Setup
To set up a Manchester or NRZ decoder, follow the general procedures to set up a decoder , choosing
Protocol Manchesteror NRZ. This will cause the following right-hand dialogs to appear next to the
Decode Setup dialog. Open each tab in turn to configure decoder settings.
B ASIC D IALOG
The Basic dialog presents the fundamental settings required for proper bit-level decoding. Configure all
Basic dialog settings:
Bit Rate - Enter the Bit Rate value here, matching the one on the bus to which you are connected as
precisely as you know it (hardware engineers working on a design often know the Bit Rate). If you are
not sure about the value, use the cursor read outs on one single bit or a sequence of bits to determine
the exact Bit Rate of your signal. The value should be correct within 5%. A mismatched Bit Rate will
cause various confusing side effects on the decoding, so it is best to take time to correctly adjust this
fundamental value. Bit Rates can be selected from 10 bits/s to 10 Gb/s. Bit Rate selection is dynamically
linked to the decoding bit rate; they are always the same value.
Idle State- Signal level (High or Low) at which there is no data transfer. The idle State complements the
Timeout value. In order to declare that a new Burst has to be started, the algorithm looks at the time
elapsed between 2 consecutive Transitions, as well as the state of the idle level between these
transitions. This mechanism allows a precise definition of what the separation gap between 2 Bursts
should be. In most cases, the idle state is specified, and therefore provides a supplementary condition to
the timeout to define the Burst start. If this distinction is not desired, select “X” in the popup box.
Polarity-. The “Polarity” governs the conversion of the physical bit state into a logical bit state. Enter the
Polarity of an NRZ signal as either Low=0 or Low=1. Note that the meaning of Polarity is slightly different
for Manchester than for NRZ: when Falling=0 is chosen, a Falling Edge through the Level will be decoded
as a logical Zero, whereas a Rising Edge through the threshold level will be decoded as a logical One;
when Falling=1 is chosen, the opposite logic applies.
(Timeout) Units - The Timeout, or Gap, separating Burst can be specified either in Bits or Seconds. Both
methods are perfectly equivalent in terms of their results, but you may vary them depending on the
context, the protocol specifications or your preference. Note that regardless of the Timeout Units
selected, the allowed Timeout range will be from 1 bit to 100 bits.
(Timeout) # Bits- When a Timeout Unit of Bits is selected, the system will use the Bit Rate to determine
the Bit Length, and multiply it by the # Bits entered here to obtain a Timeout in seconds.
(Timeout) Time - When a Timeout Unit of Seconds is selected, the system uses the number of seconds
entered here.