AN2836 Freescale Semiconductor / Motorola, AN2836 Datasheet - Page 38

• Manufacturer Part Number: AN2836
• Description: Web Server Development with MC9S12NE64 and OpenTCP
• Manufacturer: Freescale Semiconductor / Motorola

OpenTCP Project Configuration to Optimize the Stack Solution
Use Only Required Network Protocols
For resource-constrained TCP/IP stack implementations, such as implementing a TCP/IP stack on an
8-/16-bit embedded system, it is not always best to implement the complete set of networking protocols.
Figure 16
illustrates a simplified or partial TCP/IP stack implementation. This stack uses only the UDP
protocol and the user applications.
USER APPLICATION
UDP
ARP
IP
NETWORK INTERFACE
Figure 16. Partial Stack TCP/IP Stack Implementation
The major disadvantage of TCP/IP stack implementations that are customized to a specific application is
that they are not complete TCP/IP stack implementations. So, if changes to the TCP stack functionality
are required after product deployment, making updates would require recompiling the TCP stack code to
include the missing components and reprogramming the device in the field.
OpenTCP Zero Copy Functionality
Zero copy refers to the TCP/IP stack ability to send and receive from the Ethernet buffers’ stack without
copying data to user RAM. Not making a copy of the data saves user RAM space and improves
performance. Performance is improved because, in most cases, the data can be completely processed
in much less of time that would be required to make a copy of the data between the Ethernet buffer RAM
and web RAM.
Set Buffers to Appropriate Values
RAM for Tx and Rx Ethernet buffers should be balanced with user application RAM. If large Ethernet
buffers are not required for the user application, set the Ethernet buffer values (in the BUFMAP register)
so that the user application uses only the necessary RAM resources. The Tx and Rx Ethernet buffers’
size is controlled in ne64config.h .
Web Server Development with MC9S12NE64 and OpenTCP, Rev. 0
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