PM5351 datasheet(91/393 Pages) PMC

91 / 393 page

S/UNI-TETRA

PMC-Sierra, Inc.

PM5351 S/UNI-TETRA

DATASHEET

PMC-1971240

ISSUE 7

SATURN USER NETWORK INTERFACE (155-TETRA)

PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE

checking sequence (FCS) field is either a CRC-CCITT or CRC-32 function. The

CRC-CCITT is two bytes in size and has a generating polynomial g(X) = 1 + X5 +

X12 + X16. The CRC-32 is four bytes in size and has a generating polynomial

g(X) = 1 + X + X2 + X4 + X5 + X7 + X8 + X10 + X11 + X12 + X16 + X22 + X23 + X26

+ X32. The first FCS bit transmitted is the coefficient of the highest term. The

RXFP-50 implements a CRC decoder that uses a CRC encoder. The coder

registers are preset to ones. Then the packet data and CRC are feed in. The

result should be a constant number provided in the HDLC documentation. A

different value indicates an error. Packets with FCS errors are marked as such

and should be discarded by the system.

Figure 8: CRC Decoder

gn-1

Message

Dn-1

. . .

10.7.6 Performance Monitor

The Performance Monitor consists of four 16-bit saturating error event counters

and one 24-bit saturating received good packet counter. One of the error event

counters accumulates FCS errors. The second error event counter accumulates

minimum length violation packets. The third error event counter accumulates

maximum length violation packets. The fourth error event counter accumulates

aborted packets. The 24-bit receive good packet counter counts all error free

packets.

Each counter may be read through the microprocessor interface. Circuitry is

provided to latch these counters so that their values can be read while

simultaneously resetting the internal counters to 0 or 1, whichever is appropriate,

so that a new period of accumulation can begin without loss of any events. The

counters are intended to be polled at least once per second so error events will

not be missed.

The RXFP-50 monitors the packets for both minimum and maximum length

errors. When a packet size is smaller than MINPL[7:0], the packet is marked with

an error but still written into the FIFO. Misformed packets, that is packets that do

not at least contain the FCS field plus one byte, are treated differently. If a

PM5351 Datasheet(PDF) 91 Page - PMC-Sierra, Inc