KSZ8851-32MQLI Micrel Inc, KSZ8851-32MQLI Datasheet - Page 29

• Manufacturer Part Number: KSZ8851-32MQLI
• Description: IC CTLR MAC/PHY NON PCI 128PQFP
• Manufacturer: Micrel Inc

Specifications of KSZ8851-32MQLI

• Controller Type: Ethernet Controller, MAC/PHY
• Interface: Bus
• Voltage - Supply: 1.8V, 2.5V, 3.3V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 128-MQFP, 128-PQFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Supply: -
• Other names: 576-3630; KSZ8851-32MQLI

Micrel, Inc.
KSZ8851-16/32 MQL/MQLI
®
P1CR[10] to enable manual control over the pair used to transmit the LinkMD
pulse. The self-clearing cable diagnostic
test enable bit, P1SCLMD [12], is set to ‘1’ to start the test on this pair.
When bit P1SCLMD[12] returns to ‘0’, the test is complete. The test result is returned in bits P1SCLMD[14:13] and the
distance is returned in bits P1SCLMD[8:0]. The cable diagnostic test results are as follows:
00 = Valid test, normal condition
01 = Valid test, open circuit in cable
10 = Valid test, short circuit in cable
®
11 = Invalid test, LinkMD
failed
If P1SCLMD[14:13]=11, this indicates an invalid test, and occurs when the KSZ8851M is unable to shut down the link
partner. In this instance, the test is not run, as it is not possible for the KSZ8851M to determine if the detected signal is a
reflection of the signal generated or a signal from another source.
Cable distance can be approximated by the following formula:
P1SCLMD[8:0] x 0.4m for port 1 cable distance
This constant may be calibrated for different cabling conditions, including cables with a velocity of propagation that varies
significantly from the norm.
Media Access Control (MAC) Operation
The KSZ8851M strictly abides by IEEE 802.3 standards to maximize compatibility.
Inter Packet Gap (IPG)
If a frame is successfully transmitted, then the minimum 96-bit time for IPG is measured between two consecutive
packets. If the current packet is experiencing collisions, the minimum 96-bit time for IPG is measured from carrier sense
(CRS) to the next transmit packet.
Back-Off Algorithm
The KSZ8851M implements the IEEE standard 802.3 binary exponential back-off algorithm in half-duplex mode. After 16
collisions, the packet is dropped.
Late Collision
If a transmit packet experiences collisions after 512 bit times of the transmission, the packet is dropped.
Flow Control
The KSZ8851M supports standard 802.3x flow control frames on both transmit and receive sides.
On the receive side, if the KSZ8851M receives a pause control frame, the KSZ8851M will not transmit the next normal
frame until the timer, specified in the pause control frame, expires. If another pause frame is received before the current
timer expires, the timer will be updated with the new value in the second pause frame. During this period (while it is flow
controlled), only flow control packets from the KSZ8851M are transmitted.
On the transmit side, the KSZ8851M has intelligent and efficient ways to determine when to invoke flow control. The flow
control is based on availability of the system resources.
There are three programmable low watermark register FCLWR (0xB0), high watermark register FCHWR (0xB2) and
overrun watermark register FCOWR (0xB4) for flow control in RXQ FIFO. The KSZ8851M will send PAUSE frame when
the RXQ buffer hit the high watermark level (default 3.072 KByte available) and stop PAUSE frame when the RXQ buffer
hit the low watermark level (default 5.12 KByte available). The KSZ8851M will drop packet when the RXQ buffer hit the
overrun watermark level (default 256-Byte available).
The KSZ8851M issues a flow control frame (Xoff, or transmitter off), containing the maximum pause time defined in IEEE
standard 802.3x. Once the resource is freed up, the KSZ8851M sends out the another flow control frame (Xon, or
transmitter on) with zero pause time to turn off the flow control (turn on transmission to the port). A hysteresis feature is
provided to prevent the flow control mechanism from being constantly activated and deactivated.
Half-Duplex Backpressure
A half-duplex backpressure option (non-IEEE 802.3 standards) is also provided. The activation and deactivation
conditions are the same as in full-duplex mode. If backpressure is required, the KSZ8851M sends preambles to defer the
August 2009
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