This bit is always read/write ac-
cessible. XMTE is cleared by
H_RESET and is not affected by
S_RESET or setting the STOP
bit.
15
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.
3
2
POWER
RCVE
Power. When this bit is set to 1,
the device is operating in HIGH
power mode.
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).
Receive Status Enable. When
this bit is set, a value of 1 is
passed to the LEDOUT bit in this
register when there is receive ac-
tivity on the network.
This bit is read accessible al-
ways. This bit is read only; writes
have no effect. LEDOUT is unaf-
fected by H_RESET, S_RESET,
or STOP.
This bit is always read/write ac-
cessible. RCVE is set to 1 by
H_RESET and is not affected by
S_RESET or setting the STOP
bit.
14
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.).
1
0
SPEED
COLE
Speed. When this bit is set to 1,
the device is operating in HIGH
speed mode.
Collision Status Enable. When
this bit is set, a value of 1 is
passed to the LEDOUT bit in this
register when there is collision
activity on the network.
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).
This bit is always read/write ac-
cessible. COLE is cleared by
H_RESET and is not affected by
S_RESET or setting the STOP
bit.
BCR7: LED3 Status
BCR7 controls the function(s) that the LED3 pin dis-
plays. Multiple functions can be simultaneously enabled
on this LED pin. The LED display will indicate the logical
OR of the enabled functions. BCR7 defaults to Transmit
Status (XMT) with pulse stretcher enabled (PSE = 1)
and is fully programmable.
The setting of this bit will not ef-
fect the polarity of the LEDOUT
bit for this register.
Note: When LEDPE (BCR2, bit 12) is set to 1, pro-
gramming of the LED3 Status register is enabled.
When LEDPE is cleared to 0, programming of the
LED3 register is disabled. Writes to those registers will
be ignored.
This bit is always read/write ac-
cessible. LEDPOL is cleared by
H_RESET and is not affected by
S_RESET or setting the STOP
bit.
Note: Bits 15-0 in this register are programmable
through the EEPROM.
13
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
Bit
Name
Description
31-16 RES
Reserved locations. Written as
zeros and read as undefined.
Am79C978
153
AMD [ AMD ]
