User Manual

AT75C220

MAC Transmit Status Register

Access Type: Read/write

Reset Value: 0x18

• OVR

Ethernet transmit buffer overrun. Software wrote to the address register or length register when bit 4 was not 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.

• IDLE

Transmitter Idle. Asserted when the transmitter has no frame to transmit. Will be cleared when a length is written to

transmit frame length portion of the Transmit Control register. This bit is read-only.

• BNQ

Ethernet transmit buffer not queued. Software may write a new buffer address and length to the transmit DMA control-

ler. Cleared by having one frame ready to transmit and another in the process of being transmitted. This bit is read-

only.

• 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 in time. If this happens, the trans-

mitter will force bad CRC. Cleared by writing a one to this bit.

31 30 29 28 27 26 25 24

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23 22 21 20 19 18 17 16

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15 14 13 12 11 10 9 8

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76543210

– UND COMP BNQ IDLE RLE COL OVR