LAN9116_08 Datasheet, PDF (78/132 Pages) SMSC Corporation – Highly Efficient Single-Chip 10/100 Non-PCI Ethernet Controller

Highly Efficient Single-Chip 10/100 Non-PCI Ethernet Controller
Datasheet
configuration (HW_CFG) register. The TX_FIF_SZ field selects the total allocation for the TX data path,
including the TX Status FIFO size. The TX Status FIFO size is fixed at 512 Bytes (128 TX Status
DWORDs). The TX Status FIFO length is subtracted from the total TX FIFO size with the remainder
being the TX data FIFO Size. Note that TX data FIFO space includes both commands and payload
data.
RX FIFO Size is the remainder of the unallocated FIFO space (16384 bytes – TX FIFO Size). The RX
Status FIFO size is always equal to 1/16 of the RX FIFO Size. The RX Status FIFO length is subtracted
from the total RX FIFO size with the remainder being the RX data FIFO Size.
For example, if TX_FIF_SZ = 6 then:
Total TX FIFO Size = 6144 Bytes (6KB)
TX Status FIFO Size = 512 Bytes (Fixed)
TX Data FIFO Size = 6144 – 512 = 5632 Bytes
RX FIFO Size = 16384 – 6144 = 10240 Bytes (10KB)
RX Status FIFO Size = 10240 / 16 = 640 Bytes (160 RX Status DWORDs)
RX Data FIFO Size = 10240 – 640 = 9600 Bytes
Table 5.3 shows every valid setting for the TX_FIF_SZ field. Note that settings not shown in this table
are reserved and should not be used.
Note: The RX data FIFO is considered full 4 DWORDs before the length that is specified in the
HW_CFG register.
TX_FIF_SZ
2
3
4
5
6
7
8
9
10
11
12
13
14
Table 5.3 Valid TX/RX FIFO Allocations
TX DATA FIFO
SIZE (BYTES)
1536
2560
3584
4608
5632
6656
7680
8704
9728
10752
11776
12800
13824
TX STATUS FIFO
SIZE (BYTES)
512
512
512
512
512
512
512
512
512
512
512
512
512
RX DATA FIFO
SIZE (BYTES)
13440
12480
11520
10560
9600
8640
7680
6720
5760
4800
3840
2880
1920
RX STATUS FIFO
SIZE (BYTES)
896
832
768
704
640
576
512
448
384
320
256
192
128
In addition to the host-accessible FIFOs, the MAC Interface Layer (MIL) contains an additional 2K
bytes of TX, and 128 bytes of RX FIFO buffering. These sizes are fixed, and cannot be adjusted by
the host.
Revision 1.5 (07-11-08)
78
DATASHEET
SMSC LAN9116