
RELEASED 
DATASHEET 
PM7383 FREEDM-32A256
ISSUE 1 
PMC-2010336 
FRAME ENGINE AND DATA LINK MANAGER 32A256 
PROPRIETARY AND CONFIDENTIAL 
49
are serviced.  This cycle is used by the channel assigner downstream for host 
microprocessor accesses to the provisioning RAMs. 
8.3.4 Channel Assigner 
The channel assigner block determines the channel number of the data byte 
currently being processed.  The block contains a 1024 word channel provision 
RAM.  The address of the RAM is constructed from concatenating the link 
number and the time-slot number of the current data byte.  The fields of each 
RAM word include the channel number and a time-slot enable flag.  The time-slot 
enable flag labels the current time-slot as belonging to the channel indicted by 
the channel number field. 
8.3.5 Loopback Controller 
The loopback controller block implements the channel based diagnostic loopback 
function.  Every valid data byte belonging to a channel with diagnostic loopback 
enabled from the Transmit HDLC Processor / Partial Packet Buffer block 
(THDL256) is written into a 64 word FIFO.  The loopback controller monitors for 
an idle time-slot or a time-slot carrying a channel with diagnostic loopback 
enabled.  If either conditions hold, the current data byte is replaced by data 
retrieved from the loopback data FIFO. 
8.4 Receive HDLC Processor / Partial Packet Buffer 
The Receive HDLC Processor / Partial Packet Buffer block (RHDL256) 
processes up to 256 synchronous transmission HDLC data streams.  Each 
channel can be individually configured to perform flag sequence detection, bit de-
stuffing and CRC-CCITT or CRC-32 verification.  The packet data is written into 
the partial packet buffer.  At the end of a frame, packet status including CRC 
error, octet alignment error and maximum length violation are also loaded into the 
partial packet buffer.  Alternatively, a channel can be provisioned as transparent, 
in which case, the HDLC data stream is passed to the partial packet buffer 
processor verbatim. 
There is a natural precedence in the alarms detectable on a receive packet.  
Once a packet exceeds the programmable maximum packet length, no further 
processing is performed on it.  Thus, octet alignment detection, FCS verification 
and abort recognition are squelched on packets with a maximum length violation.  
An abort indication squelches octet alignment detection, minimum packet length 
violations, and FCS verification.  In addition, FCS verification is only performed