XRT72L50 Datasheet, PDF (467/471 Pages) Exar Corporation – SINGLE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

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XRT72L50
SINGLE CHANNEL DS3/E3 FRAMER WITH HDLC CONTROLLER
REV. 1.2.1
FIGURE 202. TXHDLC TIMING FOR CRC32
TxInClk
T x H D L C C lk
T xH D L C D a ta [7 :0 ]
SendMSG
SendFCS
Data Data
Data FCS FCS FCS FCS
Selecting either CRC-16 or CRC-32
The user can configure the Transmit HDLC Controller block to append either a CRC-16 or CRC-32 value to the
user-data within the outbound HDLC frame, by writing the appropriate value into Bit 5 (CRC-32 Select).
Setting this bit-field "High" configures the Transmit HDLC Controller block to append a CRC-32 value to the
user data, within the outbound HDLC frame. Conversely, setting this bit-field "Low" configures the Transmit
HDLC Controller block to append a CRC-16 value to the user data, within the outbound HDLC frame.
An illustration of the resulting outbound HDLC Frame when CRC-32 and CRC-16 is selected is shown in
Figure 203and Figure 204.
FIGURE 203. AN OUTBOUND HDLC FRAME WHEN CRC-32 IS SELECTED.
CRC-32
Trailer
User Supplied Data
HDLC Frame
FIGURE 204. AN OUTBOUND HDLC FRAME WHEN CRC-16 IS SELECTED
CRC-16
Trailer
User Supplied Data
HDLC Frame
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