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Fast Ethernet Controllers (FEC0 and FEC1)
Freescale Semiconductor
26-26
26.4.20 FIFO Receive Bound Registers (FRBR0 & FRBR1)
FRBR
n
indicates the upper address bound of the FIFO RAM. Drivers can use this value, along with the
FRSR
n
, to appropriately divide the available FIFO RAM between the transmit and receive data paths.
26.4.21 FIFO Receive Start Registers (FRSR0 & FRSR1)
FRSR
n
indicates the starting address of the receive FIFO. FRSR
n
marks the boundary between the
transmit and receive FIFOs. The transmit FIFO uses addresses from the start of the FIFO to the location
four bytes before the address programmed into the FRSR
n
. The receive FIFO uses addresses from FRSR
n
to FRBR
n
inclusive.
Hardware initializes the FRSR
n
register at reset. FRSR
n
only needs to be written to change the default
value.
Table 26-23. TFWR
n
Field Descriptions
Field
Description
31–2
Reserved, must be cleared.
1–0
TFWR
Number of bytes written to transmit FIFO before transmission of a frame begins
00 64 bytes written
01 64 bytes written
10 128 bytes written
11 192 bytes written
Address: 0xFC03_014C (FRBR0)
0xFC03_414C (FRBR1)
Access: User read-only
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
R 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1
R_BOUND
0
0
W
Reset 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 0 0 0 0 0 0 0
0
0
Figure 26-20. FIFO Receive Bound Register (FRBR
n
)
Table 26-24. FRBR
n
Field Descriptions
Field
Description
31–10
Reserved, read as 0 (except bit 10, which is read as 1).
9–2
R_BOUND
Read-only. Highest valid FIFO RAM address.
1–0
Reserved, read as 0.
Содержание MCF54455
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