Mac receive buffer queue pointer, Mac receive status register – Rainbow Electronics AT75C220 User Manual
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AT75C220
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MAC Receive Buffer Queue Pointer
Register Name: ETH_RBQP
Access Type: Read/write
Reset Value: 0x0
•
ADDRESS
Receive buffer queue pointer. Written with the address of the start of the receive queue, reads as a pointer to the cur-
rent buffer being used. The receive buffer is forced to word alignment.
MAC Receive Status Register
Register Name: ETH_RSR
Access Type: Read/write
Reset Value: 0x0
•
BNA
Buffer not available. An attempt was made to get a new buffer and the pointer indicated that it was owned by the pro-
cessor. The DMA will reread the pointer each time a new frame starts until a valid pointer is found. This bit will be set at
each attempt that fails even if it has not had a successful pointer read since it has been cleared. Cleared by writing a
one to this bit.
•
REC
Frame received. One or more frames have been received and placed in memory. Cleared by writing a one to this bit.
•
OVR
RX overrun. The DMA block was unable to store the receive frame to memory, either because the ASB bus was not
granted in time or because a not OK HRESP was returned. The buffer will be recovered if this happens. Cleared by
writing a one to this bit.
31
30
29
28
27
26
25
24
ADDRESS
23
22
21
20
19
18
17
16
ADDRESS
15
14
13
12
11
10
9
8
ADDRESS
7
6
5
4
3
2
1
0
ADDRESS
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
–
–
–
–
–
OVR
REC
BNA