KS8842-16MQL Micrel Inc, KS8842-16MQL Datasheet - Page 35
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KS8842-16MQL
Manufacturer Part Number
KS8842-16MQL
Description
IC SWITCH 10/100 16BIT 128PQFP
Manufacturer
Micrel Inc
Specifications of KS8842-16MQL
Applications
*
Mounting Type
Surface Mount
Package / Case
128-MQFP, 128-PQFP
Number Of Primary Switch Ports
2
Internal Memory Buffer Size
32
Operating Supply Voltage (typ)
3.3V
Fiber Support
Yes
Integrated Led Drivers
Yes
Phy/transceiver Interface
MII
Power Supply Type
Analog/Digital
Package Type
PQFP
Data Rate (typ)
10/100Mbps
Vlan Support
Yes
Operating Temperature (max)
70C
Operating Temperature (min)
0C
Pin Count
128
Mounting
Surface Mount
Jtag Support
No
Operating Supply Voltage (max)
3.5V
Operating Supply Voltage (min)
3.1V
Operating Temperature Classification
Commercial
Data Rate
100Mbps
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
For Use With
KS8842-PMQL-EVAL - EVAL KIT EXPERIMENTAL KS8842KS8842-16MQL-EVAL - EVAL KIT EXPERIMENTAL KS8842
Lead Free Status / RoHS Status
Not Compliant, Lead free / RoHS Compliant
Other names
576-1458
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
Switching Engine
The KSZ8842M features a high-performance switching engine to move data to and from the MAC’s packet buffers. It
operates in store and forward mode, while the efficient switching mechanism reduces overall latency.
The switching engine has a 32KB internal frame buffer. This resource is shared between all the ports. There are a total of
256 buffers available. Each buffer is sized at 128B.
MAC Operation
The KSZ8842M strictly abides by IEEE 802.3 standards to maximize compatibility. Additionally, there is an added MAC
filtering function to filter Unicast packets. The MAC filtering function is useful in applications such as VoIP where
restricting certain packets reduces congestion and thus improves performance.
Inter Packet Gap (IPG)
If a frame is successfully transmitted, 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 KSZ8842M implements the IEEE standard 802.3 binary exponential back-off algorithm in half-duplex mode, and
optional "aggressive mode" back-off. After 16 collisions, the packet is optionally dropped depending on the switch
configuration in SGCR1[8].
Late Collision
If a transmit packet experiences collisions after 512 bit times of the transmission, the packet is dropped.
Legal Packet Size
The KSZ8842M discards packets less than 64 bytes and can be programmed to accept packet size up to 1536 bytes in
SGCR2[1]. The KSZ8842M can also be programmed for special applications to accept packet size up to 1916 bytes in
SGCR2[2].
Flow Control
The KSZ8842M supports standard 802.3x flow control frames on both transmit and receive sides.
On the receive side, if the KSZ8842M receives a pause control frame, the KSZ8842M 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 KSZ8842M are transmitted.
On the transmit side, the KSZ8842M has intelligent and efficient ways to determine when to invoke flow control. The flow
control is based on availability of the system resources, including available buffers, available transmit queues, and
available receive queues.
The KSZ8842M will flow control a port that has just received a packet if the destination port resource is busy. The
KSZ8842M issues a flow control frame (Xoff), containing the maximum pause time defined in IEEE standard 802.3x. Once
the resource is freed up, the KSZ8842M sends out the other flow control frame (Xon) 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.
The KSZ8842M flow controls all ports if the receive queue becomes full.
Half-Duplex Backpressure
A half-duplex backpressure option (not in IEEE 802.3 standards) is also provided. The activation and deactivation
conditions are the same in full-duplex mode. If backpressure is required, the KSZ8842M sends preambles to defer the
other stations' transmission (carrier sense deference).
Micrel, Inc.
October 2007
35
KSZ8842-16/32 MQL/MVL/MVLI/MBL
M9999-102207-1.9