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AMD Geode™ LX Processors Data Book 37
Signal Definitions
33234H
3.4.5 PCI Interface Signals
Signal Name Ball No. Type f V Description
AD[31:0] See Table
3-6 on
page 30
I/O 33-66 Mb/s 3.3 Multiplexed Address and Data. Addresses and
data are multiplexed together on the same pins.
A bus transaction consists of an address phase
in the cycle in which FRAME# is asserted fol-
lowed by one or more data phases. During the
address phase, AD[31:0] contain a physical 32-
bit address. During data phases, AD[7:0] contain
the least significant byte (LSB) and AD[31:24]
contain the most significant byte (MSB). Write
data is stable and valid when IRDY# is asserted
and read data is stable and valid when TRDY# is
asserted. Data is transferred during the SYSREF
when both IRDY# and TRDY# are asserted.
CBE[3:0]# AH31,
AH27,
AL26,
AJ22
I/O 33-66 Mb/s 3.3 Multiplexed Command and Byte Enables. C/
BE# are the bus commands and byte enables.
During the address phase of a transaction when
FRAME# is active, C/BE# define the bus com-
mand. During the data phase C/BE# 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). The command encoding and types are
listed below:
0000: Interrupt Acknowledge
0001: Special Cycle
0010: I/O Read
0011: I/O Write
0100: Reserved
0101: Reserved
0110: Memory Read
0111: Memory Write
1000: Reserved
1001: Reserved
1010: Configuration Read
1011: Configuration Write
1100: Memory Read Multiple
1101: Dual Address Cycle (RSVD)
1110: Memory Read Line
1111: Memory Write and Invalidate
PAR AJ27 I/O 33-66 Mb/s 3.3 Parity. PAR is used with AD[31:0] and C/BE# to
generate even parity. Parity generation is
required by all PCI agents: the master drives PAR
for address and write-data phases and the target
drives PAR for read-data phases.
For address phases, PAR is stable and valid one
SYSREF after the address phase.
For data phases, PAR is stable and valid one
SYSREF 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 SYSREF after the completion of
the data phase.