Programming 53
Bits
15
through
08:
Reserved
–
These
bits
are
reserved.
Bit
07:
TX
FIFO
Empty
–
A
logic
high
(1)
indicates
the
TX
FIFO
is
currently
empty.
This
bit
provides
immediate
status
only
(not
latched)
and
is
read
‐
only.
Bit
06:
TX
FIFO
Almost
Full
–
A
logic
high
(1)
indicates
the
TX
FIFO
is
currently
almost
full.
This
bit
provides
immediate
status
only
(not
latched)
and
is
read
‐
only.
Periodic
assertion
of
this
bit
is
normal.
Bit
05:
Latched
RX
FIFO
Full
–
A
logic
high
(1)
indicates
the
RX
FIFO
has
experienced
a
full
condition
at
least
once.
This
bit
is
read
‐
only
within
this
register.
To
clear
this
condition
write
to
the
corresponding
bit
within
the
Local
Interrupt
Status
Register.
NOTE
The occurrence of the Latched RX FIFO Full signal is a fault condition due to a board malfunction
and indicates that the received data may have been lost.
Bit
04:
Latched
RX
FIFO
Almost
Full
–
A
logic
high
(1)
indicates
the
RX
FIFO
is
operating
at
the
maximum
acceptable
rate.
Under
normal
operating
conditions,
this
event
should
not
occur.
This
bit
is
read
‐
only
within
this
register.
To
clear
this
condition,
write
to
the
corresponding
bit
within
the
Local
Interrupt
Status
Register.
Bit
03:
Latched
Sync
Loss
–
A
logic
high
(1)
indicates
the
receiver
circuitry
has
detected
the
loss
of
a
valid
signal
at
least
once
since
the
last
time
the
flag
has
been
cleared.
Under
normal
operating
conditions,
this
event
should
not
occur
and
may
indicate
a
loss
of
data.
A
logic
high
may
indicate
the
receiver’s
link
was
intentionally
or
unintentionally
disconnected.
Bit
02:
RX
Signal
Detect
–
A
logic
high
(1)
indicates
the
board
receiver
is
currently
detecting
light.
This
bit
provides
immediate
status
only
(not
latched)
and
is
read
‐
only.
Bit
01:
Bad
Data
–
A
logic
high
(1)
indicates
the
board
receiver
circuit
has
detected
bad
(invalid)
data
at
least
once
since
power
up
or
since
the
flag
had
previously
been
cleared.
Under
normal
operating
conditions,
this
event
should
not
occur
and
may
indicate
a
loss
of
data.
This
bit
is
read
‐
only
within
this
register.
To
clear
this
condition,
write
to
the
corresponding
bit
within
the
Local
Interrupt
Status
Register.
Bit
00
:
Own
Data
–
A
logic
high
(1)
indicates
the
board
has
detected
the
return
of
its
own
data
packet
at
least
once
since
this
bit
has
previously
been
cleared.
This
bit
serves
as
an
indicator
that
the
link
is
intact.
The
Own
Data
bit
should
be
set
any
time
a
write
to
the
onboard
memory
occurs
or
any
time
network
interrupt
is
initiated.
This
bit
is
both
read
and
write
accessible.