Rainbow Electronics DS3131 - Manual (Page 61)

DS3131
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Table 7-D. Transmit Bit-Synchronous HDLC Functions
Zero Stuffing
Only used between opening and closing flags. Is disabled in between a closing flag
and an opening flag and for sending aborts and/or interfill data. Disabled if the
channel is set to the transparent mode.
Interfill Selection Can be either 7Eh or FFh.
Flag Generation
A programmable number of flags (1 to 16) can be set between packets. Disabled if
the channel is set to the transparent mode.
CRC Generation
Can be either CRC-16 or CRC-32 or none. Disabled if the channel is set to
transparent mode.
Invert Data
All data (including the flags and FCS) is inverted after processing. Also available in
the transparent mode.
Bit Flip
The LSB (normal mode) of the byte from the FIFO becomes the first bit sent or the
MSB (telecom mode) becomes the first bit sent. Also available in the transparent
mode.
Transparent Mode
If enabled, flag generation, zero stuffing, and FCS generation is disabled.
Passes bytes from the PCI Bus to Layer 1 on octet (byte) boundaries.
Invert FCS
When enabled, it inverts all of the bits in the FCS (useful for HDLC testing).
7.3 Bit-Synchronous HDLC Register Description
Register Name: RH[n]CR, where n= 0 to 39 (one for each port)
Register Description:
Receive HDLC Port [n] Control Register
Register Address:
See the Register Map in Section 4.5 .
Bit # 7 6 5 4 3 2 1 0
Name RABTD RCS RBF RID RCRC1 RCRC0 ROLD RTRANS
Default 0 0 0 0 0 0 0 0
Bit # 15 14 13 12 11 10 9 8
Name reserved reserved reserved reserved reserved reserved RPEN RZDD
Default 0 0 0 0 0 0 0 0
Note: Bits that are underlined are read-only; all other bits are read-write.
Bit 0/Receive Transparent Enable (RTRANS). When this bit is set low, the HDLC controller performs flag
delineation, zero destuffing, abort detection, octet length checking (if enabled via ROLD), and FCS checking (if
enabled via RCRC0/1). When this bit is set high, the HDLC controller does not perform flag delineation, zero
destuffing, and abort detection, octet length checking, or FCS checking. When in transparent mode, the device
must not be configured to write done-queue descriptors only at the end of a packet if it is desired that done-queue
descriptors be written; there is not an end of packet on the receive side in transparent mode by definition. For more
information about done-queue configuration, see Section
9.3.5 : dword 1, Bit 1/Done Queue Select (DQS). Please
note that an end of packet does not occur on the receive side while in transparent mode.
0 = transparent mode disabled
1 = transparent mode enabled