KSZ8893-MQL Micrel Semiconductor, Inc., KSZ8893-MQL Datasheet - Page 33

• Manufacturer Part Number: KSZ8893-MQL
• Description: Integrated 3-Port 10/100 Managed Switch with PHYs
• Manufacturer: Micrel Semiconductor, Inc.

The MII operates in either PHY mode or MAC mode. The data interface is a nibble wide and runs at ¼ the
network bit rate (not encoded). Additional signals on the transmit side indicate when data is valid or when an error
occurs during transmission. Similarly, the receive side has signals that convey when the data is valid and without
physical layer errors. For half duplex operation, the SCOL signal indicates if a collision has occurred during
transmission.
The KSZ8893MQL does not provide the MRXER signal for PHY mode operation and the MTXER signal for MAC
mode operation. Normally, MRXER indicates a receive error coming from the physical layer device and MTXER
indicates a transmit error from the MAC device. Since the switch filters error frames, these MII error signals are
not used by the KSZ8893MQL. So, for PHY mode operation, if the device interfacing with the KSZ8893MQL has
an MRXER input pin, it needs to be tied low. And, for MAC mode operation, if the device interfacing with the
KSZ8893MQL has an MTXER input pin, it also needs to be tied low.
RMII Interface Operation
The Reduced Media Independent Interface (RMII) specifies a low pin count Media Independent Interface (MII).
RMII provides a common interface between physical layer and MAC layer devices, and has the following key
characteristics:
1. Supports 10Mbps and 100Mbps data rates.
2. Uses a single 50 MHz clock reference (provided externally).
3. Provides independent 2-bit wide (di-bit) transmit and receive data paths.
4. Contains two distinct groups of signals: one for transmission and the other for reception
The RMII provided by the KSZ8893MQL is connected to the device’s third MAC. It complies with the RMII
Specification. The following table describes the signals used by the RMII bus. Refer to RMII Specification for full
detail on the signal description.
Micrel
November 2005
RMII
Signal Name
REF_CLK
CRS_DV
RXD1
RXD0
TX_EN
TXD1
TXD0
RX_ER
---
Direction
(with respect
to the PHY)
Input
Output
Output
Output
Input
Input
Input
Output
---
Direction
(with respect
to the MAC)
Input or
Output
Input
Input
Input
Output
Output
Output
Input
(not required)
---
Table 4: RMII Signal Description
RMII
Signal Description
Synchronous 50 MHz clock
reference for receive, transmit
and control interface
Carrier sense/
Receive data valid
Receive data bit 1
Receive data bit 0
Transmit enable
Transmit data bit 1
Transmit data bit 0
Receive error
---
33
KSZ8893MQL RMII
Signal (direction)
REFCLK (input)
SMRXDV (output)
SMRXD[1] (output)
SMRXD[0] (output)
SMTXEN (input)
SMTXD[1] (input)
SMTXD[0] (input)
(not used)
SMTXER* (input)
* Connects to RX_ER signal
of RMII PHY device
KSZ8893MQL/MQLI
M9999-111705