KS8993M Micrel Inc, KS8993M Datasheet - Page 29

• Manufacturer Part Number: KS8993M
• Description: IC SWITCH 10/100 3PORT 128PQFP
• Manufacturer: Micrel Inc

Specifications of KS8993M

• Applications: *
• Mounting Type: Surface Mount
• Package / Case: 128-MQFP, 128-PQFP
• Number Of Primary Switch Ports: 3
• Internal Memory Buffer Size: 32
• Operating Supply Voltage (typ): 1.8/2.5/3.3V
• Fiber Support: Yes
• Integrated Led Drivers: Yes
• Phy/transceiver Interface: MII/SNI
• 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): 1.89/3.465V
• Operating Supply Voltage (min): 1.71/3.135V
• Power Dissipation: 800mW
• Supply Current: 0.1/0.19A
• Operating Temperature Classification: Commercial
• Data Rate: 100Mbps
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: 576-1013 - BOARD EVAL EXPERIMENT KS8993M
• Lead Free Status / RoHS Status: Not Compliant, Lead free / RoHS Compliant

Switching Engine
The KS8993M features a high-performance switching engine to move data to and from the MACs’ packet buffers.
It operates in store and forward mode, while the efficient switching mechanism reduces overall latency.
The KS8993M has a 32kB internal frame buffer. This resource is shared between all three ports. The buffer-
sharing mode can be programmed through Global Register 2 (0x02). In one mode, ports are allowed to use any
free buffers in the buffer pool. In the second mode, each port is only allowed to use one third of the total buffer
pool. There are a total of 250 buffers available. Each buffer is sized at 128B.
MAC Operation
The KS8993M strictly abides by IEEE 802.3 standards to maximize compatibility.
Inter Packet Gap (IPG)
If a frame is successfully transmitted, the 96 bits time IPG is measured between the two consecutive MTXEN. If
the current packet is experiencing collision, the 96 bits time IPG is measured from MCRS and the next MTXEN.
Back-Off Algorithm
The KS8993M implements the IEEE standard 802.3 binary exponential back-off algorithm, and optional
"aggressive mode" back-off. After 16 collisions, the packet will be optionally dropped depending on the chip
configuration in Global Register 3 (0x03)
Late Collision
If a transmit packet experiences collisions after 512 bit times of the transmission, the packet will be dropped.
Illegal Frames
The KS8993M discards frames less than 64 bytes and can be programmed to accept frames up to 1536 bytes in
Global Register 4 (0x04). For special applications, the KS8993M can also be programmed to accept frames up to
1916 bytes in the same global register. Since the KS8993M supports VLAN tags, the maximum sizing is adjusted
when these tags are present. See the EEPROM section for programming options.
Flow Control
The KS8993M supports standard 802.3x flow control frames on both transmit and receive sides.
On the receive side, if the KS8993M receives a pause control frame, the KS8993M 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 (being flow controlled), only flow control packets from the KS8993M will be transmitted.
On the transmit side, the KS8993M 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 KS8993M will flow control a port, which just received a packet, if the destination port resource is being used
up. The KS8993M will issue a flow control frame (XOFF), containing the maximum pause time defined in IEEE
standard 802.3x. Once the resource is freed up, the KS8993M will send 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 activated and deactivated too many times.
The KS8993M will flow control all ports if the receive queue becomes full.
Half-Duplex Backpressure
A half-duplex backpressure option (Note: not in IEEE 802.3 standards) is also provided. The activation and
deactivation conditions are the same as the above in full duplex mode. If backpressure is required, the KS8993M
will send preambles to defer the other stations' transmission (carrier sense deference). To avoid jabber and
excessive deference defined in 802.3 standard, after a certain time it will discontinue the carrier sense but it will
raise the carrier sense quickly. This short silent time (no carrier sense) is to prevent other stations from sending
Micrel, Inc.
April 2005
29
KS8993M/ML/MI
M9999-041205