DS3170+ Maxim Integrated Products, DS3170+ Datasheet - Page 98

• Manufacturer Part Number: DS3170+
• Description: IC TXRX DS3/E3 100-CSBGA
• Manufacturer: Maxim Integrated Products

Specifications of DS3170+

• Function: Single-Chip Transceiver
• Interface: DS3, E3
• Number Of Circuits: 1
• Voltage - Supply: 3.135 V ~ 3.465 V
• Current - Supply: 120mA
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 100-LBGA
• Includes: DS3 Framers, E3 Framers, HDLC Controller, On-Chip BERTs
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power (watts): -

DS3170 DS3/E3 Single-Chip Transceiver
10.7.4 Transmit HDLC Overhead Processor
The Transmit HDLC Overhead Processor accepts data from the Transmit FIFO, performs bit reordering, FCS
processing, stuffing, packet abort sequence insertion, and inter-frame padding.
A byte is read from the Transmit FIFO with a packet end status. When a byte is marked with a packet end
indication, the output data stream will be padded with FFh and marked with a FIFO empty indication if the Transmit
FIFO contains less than two bytes or transmit packet start is disabled. Transmit packet start is programmable (on
or off). When the Transmit Packet Processor reads the Transmit FIFO while it is empty, the output data stream is
marked with an abort indication. Once the Transmit FIFO is empty, the output data stream will be padded with
interframe fill until the Transmit FIFO contains two or more bytes of data and transmit packet start is enabled.
Bit reordering changes the bit order of each byte. If bit reordering is disabled, the outgoing 8-bit data stream
DT[1:8] with DT[1] being the MSB and DT[8] being the LSB is input from the Transmit FIFO with the MSB in TFD[0]
and the LSB in TFD[7] of the transmit FIFO data TFD[7:0]. If bit reordering is enabled, the outgoing 8-bit data
stream DT[1:8] is input from the Transmit FIFO with the MSB in TFD[7] and the LSB in TFD[0] of the transmit FIFO
data TFD[7:0]. DT[1] is the first bit transmitted on the outgoing data stream.
FCS processing calculates an FCS and appends it to the packet. FCS calculation is a CRC-16 calculation over the
16
12
5
entire packet. The polynomial used for the CRC-16 is x
+ x
+ x
+ 1. The CRC-16 is inverted after calculation,
and appended to the packet. For diagnostic purposes, an FCS error can be inserted. This is accomplished by
appending the calculated CRC-16 without inverting it. FCS error insertion is programmable (on or off). When FCS
processing is disabled, the packet is output without appending an FCS. FCS processing is programmable (on or
off).
Stuffing inserts control data into the packet to prevent packet data from mimicking flags. Stuffing is halted during
FIFO empty periods. The 8-bit parallel data stream is multiplexed into a serial data stream, and bit stuffing is
performed. Bit stuffing consists of inserting a '0' directly following any five contiguous '1's. Stuffing is performed
from a packet start until a packet end.
Inter-frame padding inserts inter-frame fill between the packet start and end flags when the FIFO is empty. The
inter-frame fill can be flags or '1's. If the inter-frame fill is flags, flags (minimum two) are inserted until a packet start
is received. If the inter-frame fill is all '1's, an end flag is inserted, ‘1’s are inserted until a packet start is received,
and a start flag is inserted after the ‘1’s. The number of '1's between the end flag and start flag may not be an
integer number of bytes, however, the inter-frame fill will be at least 15 consecutive '1's. If the FIFO is not empty
between a packet end and a packet start, then two flags are inserted between the packet end and packet start. The
inter-frame padding type is programmable (flags or ‘1’s).
Packet abort insertion inserts a packet abort sequences as necessary. If a packet abort indication is detected, a
packet abort sequence is inserted and inter-frame padding is done until a packet start is detected. The abort
sequence is FFh.
Once all packet processing has been completed, the datastream is inserted into the DS3/E3 datastream at the
proper locations. If transmit data inversion is enabled, the outgoing data is inverted after packet processing is
performed. Transmit data inversion is programmable (on or off).
10.7.5 Receive HDLC Overhead Processor
The Receive HDLC Overhead Packet Processor accepts data from the DS3/E3 Framer and performs packet
delineation, inter-frame fill filtering, packet abort detection, destuffing, FCS processing, and bit reordering. If receive
data inversion is enabled, the incoming data is inverted before packet processing is performed. Receive data
inversion is programmable (on or off).
Packet delineation determines the packet boundary by identifying a packet start flag. Each time slot is checked for
a flag sequence (7Eh). Once a flag is found, if it is identified as a start or end flag, and the packet boundary is set.
There may be a single flag (both end and start) between packets, there may be an end flag and a start flag with a
shared zero (011111101111110) between packets, there may be an end flag and a start flag (two flags) between
packets, or there may be an end flag, inter-frame fill, and a start flag between packets. The flag check is performed
one bit at a time.
Inter-frame fill filtering removes the inter-frame fill between a start flag and an end flag. All inter-frame fill is
discarded. The inter-frame fill can be flags (01111110) or all '1's. When inter-frame fill is all ‘1’s, the number of '1's
between the end flag and the start flag may not be an integer number of bytes. When inter-frame fill is flags, the
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