Altera 8B10B Encoder/Decoder MegaCore Function - Manual (Page 26)

3–8 Chapter 3: Specifications
Parameters
8B10B Encoder/Decoder MegaCore Function User Guide May 2011 Altera Corporation
Parameters
Table 3–2 shows the 8B10B Encoder/Decoder function parameters, which can only be
set in the MegaWizard Interface (see “Parameterize” on page 2–3 ).
Signals
This section describes all interface signals.
Encoder Signals
Table 3–3 show the encoder signals.
Table 3–2. 8B10B Encoder/Decoder Parameters
Parameter Value
Mode of operation Encoder or Decoder
Register inputs/outputs
On for a three cycle latency.
Off for a one-cycle latency.
Table 3–3. Encoder Signals
Signal Name Direction Description
clk Input
Clock. The input is latched, and the result is output on this clock. There is a three clock
cycle latency between the input and output.
reset_n Input
Active low, reset. Asynchronously resets all registers in the MegaCore function. This
signal should be deasserted synchronously to the rising edge of
clk .
kin Input
Command byte indicator. When high, indicates that the input is a command byte, not a
data byte.
ena Input
Enable encoder signal. When high, indicates that the data currently present on the
datain input is to be encoded.
idle_ins Input
Idle character insert. When high, idle (K28.5) characters are inserted when ena is not
asserted.
datain[7:0] Input Data input. This is the 8-bit input word, data or command.
rdin Input
Running disparity input. When rdforce is high, the value on this pin is used as the
current running disparity instead of the internally generated one.
rdforce Input
Force running disparity. When high, the rdin value overrides the internally generated
running disparity.
kerr Output
Special K character error. This signal is set high when ena and kin are high and the
value on datain is not a valid special K character.
dataout[9:0] Output Data output. This is the 10-bit encoded output.
valid Output
Valid signal. When high, indicates that a valid encoded word is present on the
dataout output.
rdout Output
Running disparity output. The current running disparity (after encoding the word
present on the
dataout output).
rdcascade Output Cascaded running disparity. Used when encoders are cascaded.