AM79C971VCW datasheet(155/265 Pages) AMD

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Am79C971

155

P R E L I M INARY

BCR5: LED1 Status

BCR5 controls the function(s) that the LED1 pin dis-

plays. Multiple functions can be simultaneously en-

abled on this LED pin. The LED display will indicate the

logical OR of the enabled functions. BCR5 defaults to

Receive Status (RCV) with pulse stretcher enabled

(PSE = 1) and is fully programmable.

Note: When LEDPE (BCR2, bit 12) is set to 1, pro-

gramming of the LED1 Status register is enabled.

When LEDPE is cleared to 0, programming of the

LED1 register is disabled. Writes to those registers will

be ignored.

Note: Bits 15-0 in this register are programmable

through the EEPROM.

Bit

Name

Description

31-16 RES

Reserved locations. Written as

zeros and read as undefined.

LEDOUT

This bit indicates the current

(non-stretched) value of the LED

output pin. A value of 1 in this bit

indicates that the OR of the en-

abled signals is true.

The logical value of the LEDOUT

status signal is determined by the

settings of the individual Status

Enable bits of the LED register

(bits 8 and 6-0).

Read accessible always. This bit

is read only, writes have no ef-

fect. LEDOUT is unaffected by

H_RESET, S_RESET, or STOP.

LEDPOL

LED Polarity. When this bit has

the value 0, then the LED pin will

be driven to a LOW level whenev-

er the OR of the enabled signals

is true, and the LED pin will be

disabled and allowed to float high

whenever the OR of the enabled

signals is false (i.e., the LED out-

put will be an Open Drain output

and the output value will be the

inverse of the LEDOUT status

bit).

When this bit has the value 1,

then the LED pin will be driven to

a HIGH level whenever the OR of

the enabled signals is true, and

the LED pin will be driven to a

LOW level whenever the OR of

the enabled signals is false (i.e.,

the LED output will be a Totem

Pole output and the output value

will be the same polarity as the

LEDOUT status bit).

The setting of this bit will not ef-

fect the polarity of the LEDOUT

bit for this register.

Read/Write accessible always.

LEDPOL is cleared by H_RESET

and is not affected by S_RESET

or setting the STOP bit.

LEDDIS

LED Disable. This bit is used to

disable the LED output. When

LEDDIS has the value 1, then the

LED output will always be dis-

abled. When LEDDIS has the val-

ue 0, then the LED output value

will be governed by the LEDOUT

and LEDPOL values.

Read/Write accessible always.

LEDDIS is cleared by H_RESET

and is not affected by S_RESET

or setting the STOP bit.

100E

100 Mbps Enable. When this bit

is set to 1, a value of 1 is passed

to the LEDOUT bit in this register

when the Am79C971 controller is

operating at 100 Mbps mode. The

indication is valid with both the in-

ternal and external PHYs.

Read/Write accessible always.

100E is cleared by H_RESET

and is not affected by S_RESET

or setting the STOP bit.

MIISE

Media Independent Interface Se-

lected Enable. Indicates when the

MII interface is selected. This will

be set when either the Manage-

ment Port State Machine is se-

lecting the MII or when ASEL

(BCR2, bit1) is disabled and

PORTSEL (CSR15, bits 8-7) se-

lects the MII. This could control

relays to switch in and out appro-

priate filters or could control an

external PHY when sharing an

RJ45 connector.

Read/Write accessible always.

MIISE is cleared by H_RESET

and is not affected by S_RESET

or setting the STOP bit.

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