Texas Instruments TMS320C645x DSP User Manual
Page 17
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EMAC Functional Architecture
summarizes the individual EMAC and MDIO signals for the MII interface. For more information,
refer to either the IEEE 802.3 standard or ISO/IEC 8802-3:2000(E).
The EMAC module does not include a transmit error (MTXER) pin. If a transmit error occurs, CRC
inversion is used to negate the validity of the transmitted frame.
Table 2. EMAC and MDIO Signals for MII Interface
Signal Name
I/O
Description
MTCLK
I
Transmit clock (MTCLK). The transmit clock is a continuous clock that provides the timing
reference for transmit operations. The MTXD and MTXEN signals are tied to this clock. The
clock is generated by the PHY and is 2.5 MHz at 10 Mbps operation and 25 MHz at 100
Mbps operation.
MTXD[3:0]
O
Transmit data (MTXD). The transmit data pins are a collection of 4 data signals comprising 4
bits of data. MTDX0 is the least-significant bit (LSB). The signals are synchronized by MTCLK
and valid only when MTXEN is asserted.
MTXEN
O
Transmit enable (MTXEN). The transmit enable signal indicates that the MTXD pins are
generating nibble data for use by the PHY. It is driven synchronously to MTCLK.
MCOL
I
Collision detected (MCOL). The MCOL pin is asserted by the PHY when it detects a collision
on the network. It remains asserted while the collision condition persists. This signal is not
necessarily synchronous to MTCLK nor MRCLK. This pin is used in half-duplex operation
only.
MCRS
I
Carrier sense (MCRS). The MCRS pin is asserted by the PHY when the network is not idle in
either transmit or receive. The pin is de-asserted when both transmit and receive are idle.
This signal is not necessarily synchronous to MTCLK or MRCLK. This pin is used in
half-duplex operation only.
MRCLK
I
Receive clock (MRCLK). The receive clock is a continuous clock that provides the timing
reference for receive operations. The MRXD, MRXDV, and MRXER signals are tied to this
clock. The clock is generated by the PHY and is 2.5 MHz at 10 Mbps operation and 25 MHz
at 100 Mbps operation.
MRXD[3:0]
I
Receive data (MRXD). The receive data pins are a collection of 4 data signals comprising 4
bits of data. MRDX0 is the least-significant bit (LSB). The signals are synchronized by
MRCLK and valid only when MRXDV is asserted.
MRXDV
I
Receive data valid (MRXDV). The receive data valid signal indicates that the MRXD pins are
generating nibble data for use by the EMAC. It is driven synchronously to MRCLK.
MRXER
I
Receive error (MRXER). The receive error signal is asserted for one or more MRCLK periods
to indicate that an error was detected in the received frame. This is meaningful only during
data reception when MRXDV is active.
MDCLK
O
Management data clock (MDCLK). The MDIO data clock is sourced by the MDIO module on
the system. It is used to synchronize MDIO data access operations done on the MDIO pin.
The frequency of this clock is controlled by the CLKDIV bits in the MDIO control register
(CONTROL).
MDIO
I/O
Management data input output (MDIO). The MDIO pin drives PHY management data into and
out of the PHY by way of an access frame consisting of start of frame, read/write indication,
PHY address, register address, and data bit cycles. The MDIO pin acts as an output for
everything except the data bit cycles, when the pin acts as an input for read operations.
SPRU975B – August 2006
Ethernet Media Access Controller (EMAC)/Management Data Input/Output (MDIO)
17