Mac transmit status register – Rainbow Electronics AT75C220 User Manual
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AT75C220
41
MAC Transmit Status Register
Register Name: ETH_TSR
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
–
–
–
–
–
–
–
–
23
22
21
20
19
18
17
16
–
–
–
–
–
–
–
–
15
14
13
12
11
10
9
8
–
–
–
–
–
–
–
–
7
6
5
4
3
2
1
0
–
UND
COMP
BNQ
IDLE
RLE
COL
OVR