Signal Definitions

32581C

3.4.6PCI Bus Interface Signals (Continued)

Signal Name

BalL No.

Type

Description

Mux

 

 

 

 

 

LOCK#

H3

I/O

Lock Operation. LOCK# indicates an atomic operation

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that may require multiple transactions to complete. When

 

 

 

 

LOCK# is asserted, non-exclusive transactions may pro-

 

 

 

 

ceed to an address that is not currently locked (at least

 

 

 

 

16 bytes must be locked). A grant to start a transaction

 

 

 

 

on PCI does not guarantee control of LOCK#. Control of

 

 

 

 

LOCK# is obtained under its own protocol in conjunction

 

 

 

 

with GNT#.

 

 

 

 

It is possible for different agents to use PCI while a single

 

 

 

 

master retains ownership of LOCK#. The arbiter can

 

 

 

 

implement a complete system lock. In this mode, if

 

 

 

 

LOCK# is active, no other master can gain access to the

 

 

 

 

system until the LOCK# is de-asserted.

 

 

 

 

This signal is internally connected to a pull-up resistor.

 

 

 

 

 

 

DEVSEL#

E4

I/O

Device Select. DEVSEL# indicates that the driving

BHE#

 

 

 

device has decoded its address as the target of the cur-

 

 

 

 

rent access. As an input, DEVSEL# indicates whether

 

 

 

 

any device on the bus has been selected. DEVSEL# is

 

 

 

 

also driven by any agent that has the ability to accept

 

 

 

 

cycles on a subtractive decode basis. As a master, if no

 

 

 

 

DEVSEL# is detected within and up to the subtractive

 

 

 

 

decode clock, a master abort cycle is initiated (except for

 

 

 

 

special cycles which do not expect a DEVSEL#

 

 

 

 

returned).

 

 

 

 

This signal is internally connected to a pull-up resistor.

 

 

 

 

 

 

PERR#

H2

I/O

Parity Error. PERR# is used for reporting data parity

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errors during all PCI transactions except a Special Cycle.

 

 

 

 

The PERR# line is driven two PCI clocks after the data in

 

 

 

 

which the error was detected. This is one PCI clock after

 

 

 

 

the PAR that is attached to the data. The minimum dura-

 

 

 

 

tion of PERR# is one PCI clock for each data phase in

 

 

 

 

which a data parity error is detected. PERR# must be

 

 

 

 

driven high for one PCI clock before being placed in TRI-

 

 

 

 

STATE. A target asserts PERR# on write cycles if it has

 

 

 

 

claimed the cycle with DEVSEL#. The master asserts

 

 

 

 

PERR# on read cycles.

 

 

 

 

This signal is internally connected to a pull-up resistor.

 

 

 

 

 

 

SERR#

H1

I/O

System Error. SERR# can be asserted by any agent for

---

 

 

 

reporting errors other than PCI parity. When the PFS bit

 

 

 

 

is enabled in the GX1 module’s PCI Control Function 2

 

 

 

 

register (Index 41h[5]), SERR# is asserted upon asser-

 

 

 

 

tion of PERR#.

 

 

 

 

This signal is internally connected to a pull-up resistor.

 

 

 

 

 

 

AMD Geode™ SC3200 Processor Data Book

55

Page 55
Image 55
AMD SC3200 manual Lock#, Devsel#, Bhe#, Serr#