IPSERIALLITE Altera, IPSERIALLITE Datasheet - Page 69

• Manufacturer Part Number: IPSERIALLITE
• Manufacturer: Altera

Specifications of IPSERIALLITE

• Lead Free Status / RoHS Status: Not Compliant

Specifications
Altera Corporation
August 2005
Enabled
Disabled
Table 3–23. CRC Options
Option
CRC logic is created. CRC usage is specified independently for each port.
CRC logic is not created. CRC usage is specified independently for each port. This
is the default CRC setting.
The 16-bit version provides excellent protection for packets smaller than
about 1K bytes. For larger packets, CRC-32 can be considered, but it
requires significantly more logic, especially on implementations
requiring many lanes. At 16 lanes, CRC-32 logic may constitute as much
as half of the logic of the entire SerialLite instantiation. Therefore CRC-32
should only be used when absolutely necessary.
1
Half Duplex
If you want to reduce the amount of logic used for implementing CRC
logic, there are situations where you can cut it approximately in half. The
SerialLite protocol specifies a symmetric full-duplex link, where traffic is
passed in both directions. There may be applications, however, where the
traffic in one direction is qualitatively different from that in the other
direction. For instance, payload data may travel in one direction, with
system messages or acknowledgments coming in the reverse direction.
In such systems, you may only be concerned about the data integrity in
one direction. The Parameterize - SerialLite MegaCore function wizard
allows you to specify, for a given application, to generate a CRC on
transmission, but not to check on reception. Conversely, you can specify
to check a CRC on reception, but not to generate on transmission. It is
important that both ends of the link match each other. So if the near-end
logic generates CRC, then the far-end logic must check CRC, and vice
versa.
The wizard allows you to make this selection by asking which direction
you wish to protect with CRC. The default provides protection in both
directions. Alternatively, you can select to protect only the transmit (TX)
direction or the receive (RX) direction. You decide independently for each
port which directions you wish to protect.
Tables 3–23
MegaCore Function Version 1.1.0
Because of the 256-byte packet size limitation, CRC-32 is never
really needed on the priority data port (although it is available).
through
3–25
show the different CRC options.
Description
SerialLite MegaCore Function User Guide
3–37