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GD82559ER — Networkin
g
Silicon
8
Datasheet
3.2.2 Interface Control Si
g
nals
Symbol Type Name and Function
FRAME# S/T/S
Cycle Frame.
The c
y
cle frame si
g
nal is driven b
y
the current master
to indicate the be
g
innin
g
and duration of a transaction. FRAME# is
asserted to indicate the start of a transaction and de-asserted durin
g
the final data phase.
IRDY# S/T/S
Initiator Ready.
The initiator read
y
si
g
nal indicates the bus master’s
abilit
y
to complete the current data phase and is used in con
j
unction
with the tar
g
et read
y
(
TRDY#
)
si
g
nal. A data phase is completed on
an
y
clock c
y
cle where both IRDY# and TRDY# are sampled asserted
(
low
)
simultaneousl
y
.
TRDY# S/T/S
Target Ready.
The tar
g
et read
y
si
g
nal indicates the selected device’s
abilit
y
to complete the current data phase and is used in con
j
unction
with the initiator read
y
(
IRDY#
)
si
g
nal. A data phase is completed on
an
y
clock c
y
cle where both IRDY# and TRDY# are sampled asserted
(
low
)
simultaneousl
y
.
STOP# S/T/S
Stop.
The stop si
g
nal is driven b
y
the tar
g
et to indicate to the initiator
that it wishes to stop the current transaction. As a bus slave, STOP# is
driven b
y
the 82559ER to inform the bus master to stop the current
transaction. As a bus master, STOP# is received b
y
the 82559ER to
stop the current transaction.
IDSEL IN
Initialization Device Select.
The initialization device select si
g
nal is
used b
y
the 82559ER as a chip select durin
g
PCI confi
g
uration read
and write transactions. This si
g
nal is provided b
y
the host in PCI
s
y
stems.
DEVSEL# S/T/S
Device Select.
The device select si
g
nal is asserted b
y
the tar
g
et once
it has detected its address. As a bus master, the DEVSEL# is an input
si
g
nal to the 82559ER indicatin
g
whether an
y
device on the bus has
been selected. As a bus slave, the 82559ER asserts DEVSEL# to
indicate that it has decoded its address as the tar
g
et of the current
transaction.
REQ# T/S
Request.
The re
q
uest si
g
nal indicates to the bus arbiter that the
82559ER desires use of the bus. This is a point-to-point si
g
nal and
ever
y
bus master has its own REQ#.
GNT# IN
Grant.
The
g
rant si
g
nal is asserted b
y
the bus arbiter and indicates to
the 82559ER that access to the bus has been
g
ranted. This is a point-
to-point si
g
nal and ever
y
master has its own GNT#.
INTA# O/D
Interrupt A.
The interrupt A si
g
nal is used to re
q
uest an interrupt b
y
the 82559ER. This is an active low, level tri
gg
ered interrupt si
g
nal.
SERR# O/D
System Error.
The s
y
stem error si
g
nal is used to report address
parit
y
errors. When an error is detected, SERR# is driven low for a
sin
g
le PCI clock.
PERR# S/T/S
Parity Error.
The parit
y
error si
g
nal is used to report data parit
y
errors
durin
g
all PCI transactions except a Special C
y
cle. The parit
y
error pin
is asserted two clock c
y
cles after the error was detected b
y
the device
receivin
g
data. The minimum duration of PERR# is one clock for each
data phase where an error is detected. A device cannot report a parit
y
error until it has claimed the access b
y
assertin
g
DEVSEL# and
completed a data phase.