Datasheet

554

SAM7X Series [DATASHEET]

6120K–ATARM–11-Feb-14

37.5.4 Transmit Status Register

Access Type: Read-write

This register, when read, provides details of the status of a transmit. Once read, individual bits may be cleared by writing 1 to

them. It is not possible to set a bit to 1 by writing to the register.

• UBR: Used Bit Read

Set when a transmit buffer descriptor is read with its used bit set. Cleared by writing a one to this bit.

• COL: Collision Occurred

Set by the assertion of collision. Cleared by writing a one to this bit.

• RLE: Retry Limit exceeded

Cleared by writing a one to this bit.

• TGO: Transmit Go

If high transmit is active.

• BEX: Buffers exhausted mid frame

If the buffers run out during transmission of a frame, then transmission stops, FCS shall be bad and tx_er asserted. Cleared by

writing a one to this bit.

• COMP: Transmit Complete

Set when a frame has been transmitted. Cleared by writing a one to this bit.

• UND: Transmit Underrun

Set when transmit DMA was not able to read data from memory, either because the bus was not granted in time, because a not

OK hresp(bus error) was returned or because a used bit was read midway through frame transmission. If this occurs, the

transmitter forces bad CRC. Cleared by writing a one to this bit.

31 30 29 28 27 26 25 24

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15 14 13 12 11 10 9 8

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76543210

– UND COMP BEX TGO RLE COL UBR