ICS1894-32
10BASE-T/100BASE-TX INTEGRATED PHYCEIVER WITH RMII INTERFACE PHYCEIVER
IDT®
10BASE-T/100BASE-TX INTEGRATED PHYCEIVER WITH RMII INTERFACE 6
ICS1894-32 REV M 021512
Note: As per the ISO/IEC standard, the
ICS1894-32 does not affect, nor is it
affected by, the underlying structure of the
MAC frame it is conveying.
100Base-TX Operation
During 100Base-TX data transmission, the ICS1894-32
accepts packets from the MAC and inserts Start-of-Stream
Delimiters (SSDs) and End-of-Stream Delimiters (ESDs)
into the data stream. The ICS1894-32 encapsulates each
MAC frame, including the preamble, with an SSD and an
ESD. As per the ISO/IEC Standard, the ICS1894-32
replaces the first octet of each MAC preamble with an SSD
and appends an ESD to the end of each MAC frame.
When receiving data from the medium, the ICS1894-32
removes each SSD and replaces it with the pre-defined
preamble pattern before presenting the data on the MAC
Interface. When the ICS1894-32 encounters an ESD in the
received data stream, signifying the end of the frame, it ends
the presentation of data on the MAC Interface. Therefore,
the local MAC receives an unaltered copy of the transmitted
frame sent by the remote MAC.
During periods when MAC frames are being neither
transmitted nor received, the ICS1894-32 signals and
detects the IDLE condition on the Link Segment. In the
100Base-TX mode, the ICS1894-32 transmit channel sends
a continuous stream of scrambled ones to signify the IDLE
condition. Similarly, the ICS1894-32 receive channel
continually monitors its data stream and looks for a pattern
of scrambled ones. The results of this signaling and
monitoring provide the ICS1894-32 with the means to
establish the integrity of the Link Segment between itself
and its remote link partner and inform its Station
Management Entity (SME) of the link status.
10Base-T Operation
During 10Base-T data transmission, the ICS1894-32 inserts
only the IDL delimiter into the data stream. The ICS1894-32
appends the IDL delimiter to the end of each MAC frame.
However, since the 10Base-T preamble already has a
Start-of-Frame delimiter (SFD), it is not required that the
ICS1894-32 insert an SSD-like delimiter.
When receiving data from the medium (such as a
twisted-pair cable), the ICS1894-32 uses the preamble to
synchronize its receive clock. When the ICS1894-32
receive clock establishes lock, it presents the preamble
nibbles to the MAC Interface.
In 10M operations, during periods when MAC frames are
being neither transmitted nor received, the ICS1894-32
signals and detects Normal Link Pulses. This action allows
the integrity of the Link Segment with the remote link partner
to be established and then reported to the ICS1894-32’s
SME.
Auto-Negotiation
The ICS1894-32 conforms to the auto-negotiation protocol,
defined in Clause 28 of the IEEE 802.3u specification.
Autonegotiation is enabled by either hardware pin strapping
(pin 20) or software (register 0h bit 12).
Auto-negotiation allows link partners to select the highest
common mode of operation. Link partners advertise their
capabilities to each other, and then compare their own
capabilities with those they received from their link partners.
The highest speed and duplex setting that is common to the
two link partners is selected as the mode of operation.
The following list shows the speed and duplex operation
mode from highest to lowest.
• Priority 1: 100Base-TX, full-duplex
• Priority 2: 100Base-TX, half-duplex
• Priority 3: 10Base-T, full-duplex
• Priority 4: 10Base-T, half-duplex
If auto-negotiation is not supported or the ICS1894-32 link
partner is forced to bypass auto-negotiation, the
ICS1894-32 sets its operating mode by observing the signal
at its receiver. This is known as parallel detection, and
allows the ICS1894-32 to establish link by listening for a
fixed signal protocol in the absence of auto-negotiation
advertisement protocol.
MII Management (MIIM) Interface
The ICS1894-32 supports the IEEE 802.3 MII Management
Interface, also known as the Management Data Input /
Output (MDIO) Interface. This interface allows upper-layer
devices to monitor and control the state of the ICS1894-32.
An external device with MIIM capability is used to read the
PHY status and/or configure the PHY settings. Additional
details on the MIIM interface can be found in Clause
22.2.4.5 of the IEEE 802.3u Specification.
