ICS1893BF Data Sheet Rev. E - Release
Chapter 7 Management Register Set
7.2.5 Low Power Mode (bit 0.11)
This bit provides one way to control the ICS1893BF low-power mode function. When bit 0.11 is logic:
• Zero, there is no impact to ICS1893BF operations.
• One, the ICS1893BF enters the low-power mode. In this case, the ICS1893BF disables all internal
functions and drives all MAC output pins low except for those that support the MII Serial Management
Port. In addition, the ICS1893BF internally activates the TPTRI function to tri-state the signals on the
Twisted-Pair Transmit pins (TP_TXP and TP_TXN) and achieve additional power savings.
Note: There are two ways the ICS1893BF can enter low-power mode. When entering low-power mode:
• By setting bit 0.11 to logic one, the ICS1893BF maintains the value of all Management Register
bits except the latching high (LH) and latching low (LL) status bits, which are re-initialized to their
default values instead. (For more information on latching high and latching low bits, see Section
7.1.4.1, “Latching High Bits” and Section 7.1.4.2, “Latching Low Bits”.)
• During a reset, the ICS1893BF sets all management register bits to their default values.
7.2.6 Isolate (bit 0.10)
This bit controls the ICS1893BF Isolate function. When bit 0.10 is logic:
• Zero, there is no impact to ICS1893BF operations.
• One, the ICS1893BF electrically isolates its data paths from the MAC Interface. The ICS1893BF places
all MAC output signals (TXCLK, RXCLK, RXDV, RXER, RXD[3:0], COL, and CRS) in a high-impedance
state and it isolates all MAC input signals (TXD[3:0], TXEN, and TXER). In this mode, the Serial
Management Interface continues to operate normally (that is, bit 0.10 does not affect the Management
Interface).
The default value for bit 0.10 depends upon the PHY address of Table 7-16. If the PHY address:
• Is equal to 00000b, then the default value of bit 0.10 is logic one, and the ICS1893BF isolates itself from
the MAC Interface.
• Is not equal to 00000b, then the default value of bit 0.10 is logic zero, and the ICS1893BF does not
isolate its MAC Interface.
7.2.7 Restart Auto-Negotiation (bit 0.9)
This bit allows an STA to restart the auto-negotiation process in Software mode (that is, the HW/SW pin is
logic one). When bit 0.12 is logic:
• Zero, the Auto-Negotiation sublayer is disabled, and the ICS1893BF isolates any attempt by the STA to
set bit 0.9 to logic one.
• One (as set by an STA), the ICS1893BF restarts the auto-negotiation process. Once the auto-negotiation
process begins, the ICS1893BF automatically sets this bit to logic zero, thereby providing the
self-clearing feature.
ICS1893BF, Rev. E, 8/11/09
August, 2009
Copyright © 2009, IDT, Inc.
All rights reserved.
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