TNETX3150 datasheet(66/113 Pages) TI1

66 / 113 page

TNETX3150/TNETX3150A

ThunderSWITCH™ 15-PORT 10-/100-MBIT/S ETHERNET™ SWITCH

SPWS027F – FEBRUARY 1997 – REVISED SEPTEMBER 1997

POST OFFICE BOX 655303

• DALLAS, TEXAS 75265

port structures (continued)

D The immediate queue collates the cut-through-mode buffer information. If there is data queued to the

immediate queue and the port is available, the data is transmitted. New frame data is placed onto the

immediate queue only when the following conditions exist:

–

Data can cut through from source to destination.

–

The transmitter is currently idle on the destination port.

–

There is no existing frame transfer occurring on either transmit queue or immediate queue.

If the number of buffers in the buffer pool becomes less than or equal to zero, no further data is accepted. RX

frame data is discarded until the free queue contains free buffers again. Additionally, individual queues can

overflow, in particular the transmit queue. The transmit queue length is recorded as a residual figure (i.e.,

number of buffers remaining rather than number of buffers queued). If this becomes negative, no further frame

data is queued and frames are discarded.

QM for cut-through operation (see Figure 25)

Free Queue Register

Working Register

List Of Empty External DRAM Buffers

Four-Entry,

Free-Buffer Stack

Channel 0

Channel 1

Channel 14

Channel 0

Channel 1

Channel 14

Length

Tail

Head

Tail

Length

Immediate

Queue for

Other

Channels

RX FIFO Buffers

Immediate queue

for channel 14

1. RX FIFO buffer

archived to external

DRAM buffer.

TX FIFO Buffers

5. Free buffer returned

to the working buffer,

first entry in the stack,

or to the free queue if

stack is full.

2. Full FIFO buffer transferred to DRAM buffer

(destination channel 14). The next free buffer in

free queue or free buffer stack is used.

3. Buffer linked to

tail of the

destination

immediate queue.

4. External buffer

moved from DRAM

to the TX FIFO and

transmitted.

Figure 25. QM for Cut-Through

TNETX3150 数据表(PDF) 66 Page - Texas Instruments

TNETX3150 数据表(HTML) 66 Page - Texas Instruments

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

数据表下载