ICS1893CF datasheet(49/127 Pages) RENESAS

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Chapter 7 Management Register Set

ICS1893CF, Rev. K, 05/13/10

May, 2010

ICS1893CF Data Sheet Rev. J - Release

7.2.8 Duplex Mode (bit 0.8)

This bit provides a means of controlling the ICS1893CF Duplex Mode. Its operation depends on several

other functions, including the HW/SW input pin and the Auto-Negotiation Enable bit (bit 0.12). When the

ICS1893CF is configured for:

• Hardware mode (that is, the HW/SW pin is logic zero), the ICS1893CF isolates bit 0.8 and uses the

DPXSEL input pin to establish the Duplex mode for the ICS1893CF. In this Hardware mode:

– Bit 0.8 is undefined.

– The ICS1893CF provides a Duplex Mode Status bit (in the QuickPoll Detailed Status Register, bit

17.14), which always shows the setting of an active link.

• Software mode (that is, the HW/SW pin is logic one), the function of bit 0.8 depends on the

Auto-Negotiation Enable bit, 0.12. When the auto-negotiation process is:

– Enabled, the ICS1893CF isolates bit 0.8 and relies upon the results of the auto-negotiation process

to establish the duplex mode.

– Disabled, bit 0.8 determines the Duplex mode. Setting bit 0.8 to logic:

• Zero selects half-duplex operations.

• One selects full-duplex operations. (When the ICS1893CF is operating in Loopback mode, it

isolates bit 0.8, which has no effect on the operation of the ICS1893CF.)

7.2.9 Collision Test (bit 0.7)

This bit controls the ICS1893CF Collision Test function. When an STA sets bit 0.7 to logic:

• Zero, the ICS1893CF disables the collision detection circuitry for the Collision Test function. In this case,

the COL signal does not track the TXEN signal. (The default value for this bit is logic zero, that is,

disabled.)

• One, as per the ISO/IEE 8802-3 standard, clause 22.2.4.1.9, the ICS1893CF enables the collision

detection circuitry for the Collision Test function, even if the ICS1893CF is in Loopback mode (that is, bit

0.14 is set to 1). In this case, the Collision Test function tracks the Collision Detect signal (COL) in

response to the TXEN signal. The ICS1893CF asserts the Collision signal (COL) within 512 bit times of

receiving an asserted TXEN signal, and it de-asserts COL within 4 bit times of the de-assertion of the

TXEN signal.

7.2.10 IEEE Reserved Bits (bits 0.6:0)

The IEEE reserves these bits for future use. When an STA:

• Reads a reserved bit, the ICS1893CF returns a logic zero.

• Writes to a reserved bit, it must use the default value specified in this data sheet.

The ICS1893CF uses some reserved bits to invoke auxiliary functions. To ensure proper operation of the

ICS1893CF, an STA must maintain the default value of these bits. Therefore, ICS recommends that during

any STA write operation, an STA write the default value to all reserved bits, even those bits that are Read

Only.

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