DS3171N+ Maxim Integrated Products, DS3171N+ Datasheet - Page 98

• Manufacturer Part Number: DS3171N+
• Description: TXRX SGL DS3/E3 400PBGA
• Manufacturer: Maxim Integrated Products

Specifications of DS3171N+

• Function: Single-Chip Transceiver
• Interface: DS3, E3
• Number Of Circuits: 1
• Voltage - Supply: 3.135 V ~ 3.465 V
• Current - Supply: 273mA
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 400-BGA
• Includes: DS3 Framers, E3 Framers, HDLC Controller, On-Chip BERTs
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power (watts): -
• Other names: 90-31710+N00

DS3171/DS3172/DS3173/DS3174
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
number of bits between the end flag and the start flag will be an integer number of bytes (flags). Any time there is
less than 16 bits between two flags, the data will be discarded.
Packet abort detection searches for a packet abort sequence. Between a packet start flag and a packet end flag, if
an abort sequence is detected, the packet is marked with an abort indication, and all subsequent data is discarded
until a packet start flag is detected. The abort sequence is seven consecutive ones.
Packet abort detection searches for a packet abort sequence. Between a packet start flag and a packet end flag, if
an abort sequence is detected, the packet is marked with an abort indication, and all subsequent data is discarded
until a packet start flag is detected. The abort sequence is seven consecutive ones.
Destuffing removes the extra data inserted to prevent data from mimicking a flag or an abort sequence. After a start
flag is detected, destuffing is performed until an end flag is detected. Destuffing consists of discarding any '0' that
directly follows five contiguous '1's. After destuffing is completed, the serial bit stream is demultiplexed into an 8-bit
parallel data stream and passed on with packet start, packet end, and packet abort indications. If there is less than
eight bits in the last byte, an invalid packet status is set, and the packet is tagged with an abort indication. If a
packet ends with five contiguous '1's, the packet will be processed as a normal packet regardless of whether or not
the five contiguous '1's are followed by a '0'.
FCS processing checks the FCS, discards the FCS bytes, and marks FCS erred packets. The FCS is checked for
errors, and the last two bytes are removed from the end of the packet. If an FCS error is detected, the packet is
marked with an FCS error indication. The HDLC CONTROLLER performs FCS-16 checking. FCS processing is
programmable (on or off). If FCS processing is disabled, FCS checking is not performed, and all of the packet data
is passed on.
Bit reordering changes the bit order of each byte. If bit reordering is disabled, the incoming 8-bit data stream
DT[1:8] with DT[1] being the MSB and DT[8] being the LSB is output to the Receive FIFO with the MSB in RFD[0]
and the LSB in RFD[7] of the receive FIFO data RFD[7:0]. If bit reordering is enabled, the incoming 8-bit data
stream DT[1:8] is output to the Receive FIFO with the MSB in RFD[7] and the LSB in RFD[0] of the receive FIFO
data RFD[7:0]. DT[1] is the first bit received from the incoming data stream.
Once all of the packet processing has been completed, The 8-bit parallel data stream is passed on to the Receive
FIFO with packet start, packet end, and packet error indications.
10.7.6 Receive FIFO
The Receive FIFO block contains memory for 256 bytes of data with data status information and controller circuitry
for reading and writing the memory. The Receive FIFO Controller controls filling the memory, tracking the memory
fill level, maintaining the memory read and write pointers, and detecting memory overflow and underflow
conditions. The Receive FIFO accepts data and data status from the Receive Packet Processor and stores the
data along with data status information in memory. The data is read from the receive FIFO via the microprocessor
interface. The Receive FIFO also outputs FIFO fill status (empty/data available/full) via the microprocessor
interface. All operations are byte based. The Receive FIFO is considered empty when it does not contain any data.
The Receive FIFO is considered to have data available when there is a programmable number of bytes or more
stored in the memory. The Receive FIFO is considered full when it does not have any space available for storage.
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