at91sam9g20-cu ATMEL Corporation, at91sam9g20-cu Datasheet - Page 644

• Manufacturer Part Number: at91sam9g20-cu
• Description: At91 Arm Thumb Microcontrollers
• Manufacturer: ATMEL Corporation

36.5.5
Register Name:
Access Type:
This register points to the entry in the receive buffer queue (descriptor list) currently being used. It is written with the start
location of the receive buffer descriptor list. The lower order bits increment as buffers are used up and wrap to their original
values after either 1024 buffers or when the wrap bit of the entry is set.
Reading this register returns the location of the descriptor currently being accessed. This value increments as buffers are
used. Software should not use this register for determining where to remove received frames from the queue as it con-
stantly changes as new frames are received. Software should instead work its way through the buffer descriptor queue
checking the used bits.
Receive buffer writes also comprise bursts of two words and, as with transmit buffer reads, it is recommended that bit 2 is
always written with zero to prevent a burst crossing a 1K boundary, in violation of section 3.6 of the AMBA specification.
• ADDR:
Written with the address of the start of the receive queue, reads as a pointer to the current buffer being used.
644
31
23
15
7
AT91SAM9G20 Preliminary
Receive buffer queue pointer address
Receive Buffer Queue Pointer Register
30
22
14
EMAC_RBQP
Read-write
6
29
21
13
5
ADDR
28
20
12
4
ADDR
ADDR
ADDR
27
19
11
3
26
18
10
2
25
17
9
1
–
6384B–ATARM–15-Dec-08
24
16
8
0
–