KS8721SL A4 Micrel Inc, KS8721SL A4 Datasheet - Page 14

• Manufacturer Part Number: KS8721SL A4
• Manufacturer: Micrel Inc

Specifications of KS8721SL A4

• Lead Free Status / RoHS Status: Not Compliant

KS8721BL/SL
Transmit Data [1:0] (TXD[1:0])
Transmit Data TXD[1:0] transitions synchronously with respect to REF_CLK. When TX_EN is asserted, TXD[1:0] are ac-
cepted for transmission by the PHY. TXD[1:0] remains as “00” to indicate idle when TX_EN is de-asserted. Values of TXD[1:0]
other than “00” when TX_EN is de-asserted are reserved for out-of-band signalling (to be defined). Values other than “00”
on TXD[1:0] while TX_EN is de-asserted are ignored by the PHY.
Collision Detection
Since the definition of CRS_DV and TX_EN both contain an accurate indication of the start of frame, the MAC reliably re-
generates the COL signal of the MII by ANDing TX_EN and CRS_DV.
During the IPG time following the successful transmission of a frame, the COL signal is asserted by some transceivers as
a self-test. The Signal Quality Error (SQE) function is not supported by the reduced MII due to the lack of the COL signal.
Historically, SQE was present to indicate that a transceiver located physically remote from the MAC was functioning. Since
the reduced MII only supports chip-to-chip connections on a PCB, SQE functionality is not required.
RX_ER
The PHY provides RX_ER as an output according to the rules specified in IEEE 802.3u [2] (see Clause 24, Figure 24-
11– Receive State Diagram). RX_ER is asserted for one or more REF_CLK periods to indicate that an error (e.g., a coding
error or any error that a PHY is capable of detecting, and that may otherwise be undetectable by the MAC sublayer) is de-
tected somewhere in the frame presently being transferred from the PHY. RX_ER transitions synchronously with respect to
REF_CLK. While CRS_DV is de-asserted, RX_ER has no effect on the MAC.
RMII AC Characteristics
Unused RMII Pins
Input Pins
Output Pins
M9999-022105
Symbol
t
t
SU
H
Parameter
REF_CLK Frequency
REF_CLK Duty Cycle
TXD[1:0], TX_EN, RXD[1:0], CRS_DV, RXER
TXD[1:0], TX_EN, RXD[1:0], CRS_DV, RXER
Data Hold from REF_CLK
Rising Edge
TXD[2:3] and TXER are pull-down to GND.
RXD[2:3] and RXC are no connect.
Note that the RMII pin needs to be pulled up to enable RMII mode.
14
Min
35
4
2
Typ
50
Max
65
February 2005
MHz
Unit
Micrel
ns
ns
%