DS33X81+ Maxim Integrated Products, DS33X81+ Datasheet - Page 92

• Manufacturer Part Number: DS33X81+
• Description: IC MAPPING ETHERNET 256CSBGA
• Manufacturer: Maxim Integrated Products

Specifications of DS33X81+

• Applications: Data Transport
• Interface: Parallel/Serial
• Voltage - Supply: 1.8V, 2.5V, 3.3V
• Package / Case: 256-CSBGA
• Mounting Type: Surface Mount
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

8.20.3.2GFP-F Linear Extension
When configured for GFP Linear Extension mode, an additional header is required. The Encapsultor’s Tag 1
Insertion function (in PP.ET1DHR and PP.ET1DLR, enabled with PP.EMCR.ET1E) is used to insert the 4-byte
GFP Extension Header value. If receiving GFP Linear Extension frames from the WAN, the PP.DMCR.DR2E bit
should be set to 1 in order to remove the incoming GFP CID, Spare, and eHEC bytes from the data stream.
Table 8-20. GFP CID/Spare/eHEC (Extension Header) Field Definition
The final two bytes of the Linear Extension Header field are used to perform header validation. The eHEC
calculation is a CRC-16 operation in which the two byte CID (and Spare) value is multiplied by X
(modulo 2) by the polynomial X
initialization value for the operation is 0x0000. The MSB of the CID is bit 16, and the resulting remainder of the
operation is the eHEC. To avoid requiring this algorithm implementation in the user’s software, several example
CID + Spare values and the corresponding eHEC values are provided in the table below.
Table 8-21. Example CID + Spare + eHEC Values
Rev: 063008
________________________________________________ DS33X162/X161/X82/X81/X42/X41/X11/W41/W11
Frame Byte Number
CID + Spare
(hex)
FF00
0000
0100
0200
0400
0800
1000
2000
4000
8000
11 & 12
9 & 10
Bit #
eHEC (hex)
CCC4
0DCC
89A9
06E6
1B98
03FF
0000
3331
6662
0373
15
15
16
14
+X
12
13
+X
5
+1. Another common representation for this polynomial is 0x1021. The
12
CID
eHEC
11
10
9
8
7
6
5
SPARE
4
eHEC
3
2
16
1
and divided
92 of 375
0
0