ICS1894-40
10BASE-T/100BASE-TX INTEGRATED PHYCEIVER WITH RMII INTERFACE
PHYCEIVER
Auto-MDI/MDIX Crossover
The ICS1894-40 includes the auto-MDI/MDIX crossover
feature. In a typical CAT 5 Ethernet installation the transmit
twisted pair signal pins of the RJ45 connector are crossed
over in the CAT 5 wiring to the partners receive twisted pair
signal pins and receive twisted pair to the partners transmit
twisted pair. This is usually accomplished in the wiring plant.
Hubs generally wire the RJ45 connector crossed to
accomplish the crossover. Two types of CAT 5 cables
(straight and crossed) are available to achieve the correct
connection. The Auto-MDI/MDIX feature automatically
corrects for miss-wired installations by automatically
swapping transmit and receive signal pairs at the PHY when
no link results. Auto-MDI/MDIX is automatic, but may be
disabled for test purposes by writing MDIO register 19 Bits
9:8 in the MDIO register. The Auto-MDI/MDIX function is
independent of Auto-Negotiation and preceeds
Auto-Negotiation when enabled.
Power Management
Clock Reference Interface
The REF_IN pin provides the ICS1894-40 Clock Reference
Interface. The ICS1894-40 requires a single clock reference
with a frequency of 25 MHz 50 parts per million. This
accuracy is necessary to meet the interface requirements of
the ISO/IEEE 8802-3 standard, specifically clauses 22.2.2.1
and 24.2.3.4. The ICS1894-40 supports two clock source
configurations: a CMOS oscillator or a CMOS driver. The
input to REF_IN is CMOS (10% to 90% VDD), not TTL.
Alternately, a 25MHz crystal may be used.
IDT™ / ICS™ 10BASE-T/100BASE-TX INTEGRATED PHYCEIVER WITH RMII INTERFACE 11
ICS1894-40
REV C 092909
IDT [ INTEGRATED DEVICE TECHNOLOGY ]
