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Signal Definitions
(Continued)
C/BE3#
V26
I/O
Multiplexed Command and Byte Enables.
During the
address phase of a transaction when FRAME# is active,
C/BE[3:0]# define the bus command. During the data
phase, C/BE[3:0]# are used as byte enables. The byte
enables are valid for the entire data phase and determine
which byte lanes carry meaningful data. C/BE0# applies
to byte 0 (LSB) and C/BE3# applies to byte 3 (MSB).
D11
C/BE2#
R26
D10
C/BE1#
G24
D9
C/BE0#
E24
D8
INTA#
AD26
I
PCI Interrupts.
The SC1100 provides inputs for the
optional “l(fā)evel-sensitive” PCI interrupts (also known in
industry terms as PIRQx#). These interrupts can be
mapped to IRQs of the internal 8259A interrupt control-
lers using PCI Interrupt Steering Registers 1 and 2
(F0 Index 5Ch and 5Dh).
---
INTB#
W24
---
INTC#
Y24
GPIO19
INTD#
V24
---
PAR
H24
I/O
Parity.
Parity generation is required by all PCI agents.
The master drives PAR for address- and write-data
phases. The target drives PAR for read-data phases. Par-
ity is even across AD[31:0] and C/BE[3:0]#.
For address phases, PAR is stable and valid one PCI
clock after the address phase. It has the same timing as
AD[31:0] but is delayed by one PCI clock.
For data phases, PAR is stable and valid one PCI clock
after either IRDY# is asserted on a write transaction or
after TRDY# is asserted on a read transaction.
Once PAR is valid, it remains valid until one PCI clock
after the completion of the data phase. (Also see
PERR#.)
D12
FRAME#
P25
I/O
Frame Cycle.
Frame is driven by the current master to
indicate the beginning and duration of an access.
FRAME# is asserted to indicate the beginning of a bus
transaction. While FRAME# is asserted, data transfers
continue. FRAME# is deasserted when the transaction is
in the final data phase.
---
IRDY#
P26
I/O
Initiator Ready.
IRDY# is asserted to indicate that the
bus master is able to complete the current data phase of
the transaction. IRDY# is used in conjunction with
TRDY#. A data phase is completed on any PCI clock in
which both IRDY# and TRDY# are sampled as asserted.
During a write, IRDY# indicates that valid data is present
on AD[31:0]. During a read, it indicates that the master is
prepared to accept data. Wait cycles are inserted until
both IRDY# and TRDY# are asserted together.
D14
TRDY#
N25
I/O
Target Ready.
TRDY# is asserted to indicate that the tar-
get agent is able to complete the current data phase of
the transaction. TRDY# is used in conjunction with
IRDY#. A data phase is complete on any PCI clock in
which both TRDY# and IRDY# are sampled as asserted.
During a read, TRDY# indicates that valid data is present
on AD[31:0]. During a write, it indicates that the target is
prepared to accept data. Wait cycles are inserted until
both IRDY# and TRDY# are asserted together.
D13
2.4.4
PCI Bus Interface Signals (Continued)
Signal Name
Ball No.
Type
Description
Mux