32579B

Signal Definitions

3.4.7PCI Bus Interface Signals (Continued)

Signal Name

BalL No.

Type

Description

Mux

 

 

 

 

 

PERR#

H2

I/O

Parity Error. PERR# is used for reporting data parity

---

 

 

 

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.

 

 

 

 

 

 

REQ1#

A5

I

Request Lines. REQ[1:0]# indicate to the arbiter that an

---

 

 

 

agent requires the bus. Each master has its own REQ#

 

REQ0#

B5

 

---

 

line. REQ# priorities (in order) are:

 

 

 

 

 

 

 

1)

VIP

 

 

 

 

2)

IDE Channel 0

 

 

 

 

3)

IDE Channel 1

 

 

 

 

4)

Audio

 

 

 

 

5)

USB

 

 

 

 

6)

External REQ0#

 

 

 

 

7)

External REQ1#.

 

 

 

 

Each REQ# is internally connected to a pull-up resistor.

 

 

 

 

 

 

GNT1#

C6

O

Grant Lines. GNT[1:0]# indicate to the requesting mas-

DID1 (Strap)

 

 

 

ter that it has been granted access to the bus. Each mas-

 

GNT0#

C5

 

DID0 (Strap)

 

ter has its own GNT# line. GNT# can be retracted at any

 

 

 

 

 

 

 

time a higher REQ# is received or if the master does not

 

 

 

 

begin a cycle within a minimum period of time (16 PCI

 

 

 

 

clocks).

 

 

 

 

Each of these signals is internally connected to a pull-up

 

 

 

 

resistor.

 

 

 

 

GNT0# must have a pull-down resistor of 1.5 KΩ, GNT1#

 

 

 

 

must have a pull-down resistor of 1.5 KΩ.

 

 

 

 

 

 

 

58

AMD Geode™ SC1200/SC1201 Processor Data Book

Page 58
Image 58
AMD SC1200, SC1201 manual Perr#, Serr#, REQ1#, REQ0#, Vip, Usb, GNT1#, GNT0#