EVB-PIC24 WIZnet, EVB-PIC24 Datasheet - Page 49

• Manufacturer Part Number: EVB-PIC24
• Description: Development Boards & Kits - PIC / DSPIC W3150A+EVAL BOARD BASED ON PIC24
• Manufacturer: WIZnet

Specifications of EVB-PIC24

• Rohs: yes
• Product: Development Kits
• Interface Type: RS-232
• Data Bus Width: 16 bit
• Dimensions: 50 mm x 40 mm

Let‟s take a brief look at Ping message before we proceed to Ping program.
Ping message has the value of „0‟(Ping Reply) or „8‟(Ping Request) at Type Field and Code Field of ICMP
Message has 0. Also, Type Dependant Data Field(4Bytes) of ICMP Message can be re-defined as ID
Field(2Bytes), Sequence Number Field(2Bytes) respectably. Data Field of ICMP Message is filled with the
Ping Data to be looped back.
Finally, it calculates the checksum of ICMP header and Ping data of which the checksum fields are 0. After
the calculation, it replaces 0 checksum fields with the newly calculated values.
<Fig 3.10> is a diagramming representation of the relationship between the ICMP Message Format and the
Ping Message.
Checking the Ping Reply about Ping Request can be done by checking if the values of ID, sequence number
and ping data field are same. In case the Ping Reply does not come back in wait time, the ping can be sent
again. In such case the Ping request is sent with the sequence number incremented by 1.
Ping Request message transmission and checking the Ping Reply message were done by ping(). The
elements of ping() are Destination IP Address, Ping Reply Wait Time, number of Ping Requests, and Ping
Data size and received Ping Replies are analyzed and processed to fit the elements.
<Fig 3.11> is the process of ping() and Ping message is defined and used as the Data Type of <Table 3-21>.
Refer to “inet/ping.h”
0
(1Byte)
Type
Type Dependent Data
ICMP Message
Checksum
(2Bytes)
(4Bytes)
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Data
7 8
<Fig 3.10: ICMP Message VS Ping Message>
(1Byte)
Code
15
0
8 or 0
Sequence Number
Ping Message
Checksum
Ping Data
(2Bytes)
(2Bytes)
7 8
ID
0
15
39