PIC16F639-E/SS【PDF 20/74 页】IC MCU FLASH 2KX14 20SSOP

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Sheet目录3876

16页 17页 18页 19页 [20页]21页 22页 23页 24页

Micrel, Inc.

KSZ8841-PMQL

October 2007

M9999-100407-1.5

Bit

Description

LS Last Segment

When set, indicates that the buffer contains the last segment of a frame.

IPCKG IP Checksum Generate

When set, the KSZ8841-PMQL will generate correct IP checksum for outgoing frames that

contains IP protocol header. The KSZ8841-PMQL supports only a standard IP header, i.e.,

IP with a 20 byte header. When this feature is used, ADD CRC bit in the transmit mode

This bit is used as a per-packet control when the IP checksum generate bit in the transmit

mode register is not set.

This bit should be always set for multiple-segment packets.

TCPCKG TCP Checksum Generate

When set, the KSZ8841-PMQL will generate correct TCP checksum for outgoing frames that

contains IP and TCP protocol header. The KSZ8841-PMQL supports only a standard IP

header, i.e., IP with a 20 byte header. When this feature is used, ADD CRC bit in the

transmit mode register should always be set.

This bit is used as a per-packet control when the TCP checksum generate bit in the transmit

mode register is not set.

This bit should be always set for multiple-segment packets.

UDPCKG UDP Checksum Generate

When set, the KSZ8841-PMQL will generate correct UDP checksum for outgoing frames that

contains an IP and UDP protocol header. The KSZ8841-PMQL supports only a standard IP

header, i.e., IP with a 20 byte header. When this feature is used, ADD CRC bit in the

transmit mode register should always be set.

This bit is used as a per-packet control when the UDP checksum generate bit in the transmit

mode register is not set.

TER Transmit End of Ring

When set, indicates that the descriptor pointer has reached its final descriptor.

The KSZ8841-PMQL returns to the base address of the list, forming a descriptor ring.

Reserved

23 – 20

SPN Switch Engine Destination Port Map

When set, this field indicates the destination port(s) where the packet will be forwarded to.

If bit 20 is set, it indicates the packet was received from port 1. If bit 21 is set, it indicates the

packet was received from port 2.

Setting all ports to 1 will cause the controller engine to broadcast the packet.

Setting all bits to 0 has no effect. The controller engine forwards the packet according to its

internal controller lookup algorithm.

This field is valid only when the last descriptor is set.

(Bits 23 and 22 are not used, but reserved for backward compatibility and future expansion.)

19 - 11

Reserved

10 - 0

TBS Transmit Buffer Size

Indicates the size, in bytes, of the transmit data buffer.

If this field is 0, the KSZ8841-PMQL ignores this buffer and moves to the next descriptor.

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