SH7619 Datasheet, PDF (684/836 Pages) Renesas Technology Corp – 32-Bit RISC Microcomputer SuperHTM RISC engine Family / SH7619 Series

Section 22 Ethernet Physical Layer Transceiver (PHY)
22.8 10Base-T Receive
The 10Base-T receiver gets the Manchester- encoded analog signal from the cable via the
magnetics. It recovers the receive clock from the signal and uses this clock to recover the NRZI
data stream. This 10M serial data is converted to 4-bit data nibbles which are passed to the
controller (EtherC) across the MII at a rate of 2.5 MHz.
This 10M receiver uses the following blocks:
• Filter and SQUELCH (analog)
• 10M PLL (analog)
• RX 10M (digital)
• MII (digital)
(1) 10M Receive Input and Squelch
The Manchester signal from the cable is fed into the core PHY (on inputs RXP and RXM) via 1:1
ratio magnetics. It is first filtered to reduce any out-of-band noise. It then passes through a
SQUELCH circuit. The SQUELCH is a set of amplitude and timing comparators that normally
reject differential voltage levels below 300mV and detect and recognize differential voltages
above 585mV.
(2) Manchester Decoding
The output of the SQUELCH goes to the RX10M block where it is validated as Manchester
encoded data. The polarity of the signal is also checked. If the polarity is reversed (local RXP is
connected to RXM of the remote partner and vice versa), then this is identified and corrected. The
10M PLL is locked onto the received Manchester signal and from this, generates the received
20MHz clock. Using this clock, the Manchester encoded data is extracted and converted to a
10MHz NRZI data stream. It is then converted from serial to 4-bit wide parallel data.
The RX10M block also detects valid 10Base-T IDLE signals, Normal Link Pulses (NLPs), to
maintain the link.
(3) 10M Receive Data across the MII
The 4 bit data nibbles are sent to the MII block. These data nibbles are valid on the rising edge of
the 2.5 MHz CO_RX_CLK.
Rev. 5.00 Mar. 15, 2007 Page 646 of 794
REJ09B0237-0500