WG82577LM S LGWR Intel, WG82577LM S LGWR Datasheet - Page 163

• Manufacturer Part Number: WG82577LM S LGWR
• Manufacturer: Intel

Specifications of WG82577LM S LGWR

• Lead Free Status / Rohs Status: Supplier Unconfirmed

Intel
10.2.1.4
10.2.1.4.1
®
5 Series Express Chipset MAC Programming Interface—82577 GbE PHY
Transmit Register Descriptions
Transmit Control Register - TCTL (0x00400; RW)
Two fields deserve special mention: CT and COLD. Software might choose to abort
packet transmission in less than the Ethernet mandated 16 collisions. For this reason,
hardware provides CT.
0
1
2
3
11:4
21:12
22
23
24
27:25
28
30:29
31
Bits
RW
RW
RO
RW
RW
RW
RW/V
RW
RW
RW
RW
RO
Type
0x0
0b
0b
0b
1b
0x0F
0x3F
0b
0b
0b
1b
01b
0b
Reset
IP Identification 15 bit (IPID15).
When set to 1b, the IP Identification field is incremented and wrapped around on
15-bit base. For example, if IP ID is equal to 0x7FFF then the next value is
0x0000; if IP ID is equal to 0xFFFF then the next value is 0x8000.
When set to 0b, the IP Identification field is incremented and wrapped around on
16-bit base. In this case, the value following 0x7FFF is 0x8000, and the value
following 0xFFFF is 0x0000.
The purpose of this feature is to enable the software to manage two sub-groups of
connections.
Enable (EN). The transmitter is enabled when this bit is set to 1b. Writing this bit
to 0b stops transmission after any in-progress packets are sent. Data remains in
the transmit FIFO until the MAC is re-enabled. Software should combine this with
reset if the packets in the FIFO should be flushed.
Reserved. Reads as 0b. Should be written to 0b for future compatibility.
Pad Short Packets (PSP). With valid data, NOT padding symbols.
0b = Do not pad
1b = Pad.
Padding makes the packet 64 bytes. This is not the same as the minimum collision
distance.
If padding of short packets is allowed, the value in Tx descriptor length field
should be not less than 17 bytes.
Collision Threshold (CT). This determines the number of attempts at re-
transmission prior to giving up on the packet (not including the first transmission
attempt). While this can be varied, it should be set to a value of 15 in order to
comply with the IEEE specification requiring a total of 16 attempts. The Ethernet
back-off algorithm is implemented and clamps to the maximum number of slot-
times after 10 retries. This field only has meaning when in half-duplex operation.
Collision Distance (COLD). Specifies the minimum number of byte times that must
elapse for proper CSMA/CD operation. Packets are padded with special symbols,
not valid data bytes. Hardware checks and pads to this value plus one byte even
in full-duplex operation. Default value is 64-byte to 512-byte times.
Software XOFF Transmission (SWXOFF). When set to a 1b, the MAC schedules the
transmission of an XOFF (PAUSE) frame using the current value of the PAUSE
timer. This bit self clears upon transmission of the XOFF frame.
Reserved.
Re-transmit on Late Collision (RTLC). Enables the MAC to re-transmit on a late
collision event.
Reserved. Used to be UNORTX and TXDSCMT in predecessors.
Reserved.
Read Request Threshold (RRTHRESH). These bits define the threshold size for the
intermediate buffer to determine when to send the read command to the packet
buffer. Threshold is defined as follow:
RRTHRESH – 00b Threshold – 2 lines of 16 bytes.
RRTHRESH – 01b Threshold – 4 lines of 16 bytes.
RRTHRESH – 10b Threshold – 8 lines of 16 bytes.
RRTHRESH – 11b Threshold – No threshold (transfer data after all of the request is
in the RFIFO).
Reserved. Reads as 0. Should be written to 0 for future compatibility.
Description
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