ICS1892Y datasheet(60/148 Pages) ICST

60 / 148 page

ICS1892, Rev. D, 2/26/01

February 26, 2001

Chapter 8

Management Register Set

ICS1892 Data Sheet

8.1.2

Management Register Bit Access

The ICS1892 Management Registers include one or more of the three following types of bits:

8.1.3

Management Register Bit Default Values

The tables in this chapter specify for each register bit the default value, if one exists. The ICS1892 sets all

Management Register bits to their default values after a reset. Table 8-4 lists the valid default values for

ICS1892 management register bits.

Note:

The ICS1892 has a number of reserved bits throughout the Management Registers. Most of these

bits provide enhanced test modes. The Management Register tables provide the default values for

these bits. The STA must not change the value of these bits under any circumstance. If the STA

inadvertently changes the default values of these reserved register bits, normal operation of the

ICS1892 can be affected.

Table 8-3.

Description of Management Register Bit Types

Management

Bit

Symbol

Description

Read-Only

An STA can obtain the value of a RO register bit. However, it cannot

alter the value of (that is, it cannot write to) an RO register bit. The

ICS1892 isolates any STA attempt to write a value to an RO bit.

Command Override

Write

An STA can read a value from a CW register bit. However, write

operations are conditional, based on the value of the Command

• Zero (the default), the ICS1892 isolates STA attempts to write to

the CW bits (that is, CW bits cannot be altered when bit 16.15 is

logic zero).

• One, the ICS1892 permits an STA to alter the value of the CW bits

in the subsequent register write. (Bit 16.15 is self-clearing and

automatically clears to zero on the subsequent write.)

Read/Write

R/W

An STA can unconditionally read from or write to a R/W register bit.

Read/Write Zero

R/W0

An STA can unconditionally read from a R/W0 register bit, but only a

‘0’ value can be written to this bit.

Table 8-4.

Range of Possible Valid Default Values for ICS1892 Register Bits

Default Condition

Default Value

–

Indicates there is no default value for the bit

Indicates the bit’s default value is logic zero

Indicates the bit’s default value is logic one

State of pin at reset

For some bits, the default value depends on the state of a particular pin at reset

(that is, the state value of a pin is latched at reset.) An example of pins that have

a default condition that depends on the state of the pin at reset are the PHY / LED

pins (P0AC, P1CL, P2LI, P3TD, and P4RD) discussed in Section 6.9, “Status

Interface”, Section 8.11, “Register 16: Extended Control Register”, and Section

9.2.2, “Multi-Function (Multiplexed) Pins: PHY Address and LED Pins”

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