Analog Devices ADSP-SC58 Series Hardware Reference Manual page 2142

NOTE: This engine does not process fragmented IP frames (IPv4 or IPv6), IP frames with security features (such
as an encapsulated security payload), and IPv6 frames with routing headers. The checksum engine bypass-
es the checksum insertion for such frames even if the checksum insertion is enabled.
The checksum is calculated for the TCP, UDP, or ICMP payload and inserted into its corresponding field in the
header. This engine can work in the following two ways.
• The TCP, UDP, or ICMPv6 pseudo-header is not included in the checksum calculation and is assumed to be
present in the checksum field of the input frame. This engine includes the checksum field in the checksum
calculation, and then replaces the checksum field with the final calculated checksum.
• The engine ignores the checksum field, includes the TCP, UDP, or ICMPv6 pseudo-header data into the
checksum calculation, and overwrites the checksum field with the final calculated value.
The status bit for the payload checksum error in the transmit descriptor word TDES0 indicates the result of this
operation. The checksum engine sets the status bit for the payload checksum error when:
• The checksum engine detects that the frame has been forwarded to the MAC transmitter engine in the store-
and-forward mode, and
• The end of frame (EOF) has not been written to the FIFO, or
• The packet ends before the number of bytes indicated by the payload length field in the IP header is received.
When the packet is longer than the indicated payload length, the COE ignores them as stuff bytes, and no error is
reported. When the engine detects the first type of error, it does not modify the TCP, UDP, or ICMP header. For
the second error type, it still inserts the calculated checksum into the corresponding header field.
Transmit checksum offloading is enabled by setting the CIC bits [23:22] of TDES0 word in the transmit descriptor.
Transmit Protocol Engine Module (TPE)
The transmit protocol engine consists of a state-machine that controls the protocol-level operation of Ethernet frame
transmission. The module performs the following functions to meet the IEEE 802.3 specifications.
• Generates preamble and SFD
• Generates carrier extension in half-duplex mode (only in RGMII mode)
• Supports frame bursting in half-duplex mode (only in RGMII mode)
• Generates jam pattern in half-duplex mode
• Contains time stamp snapshot logic for IEEE 1588 support
• Jabber timeout
• Flow control for half-duplex mode (back pressure)
• Generates transmit frame status
ADSP-SC58x/ADSP-2158x SHARC+ Processor Hardware Reference
EMAC CORE Transmission Engine
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