PCI9080 Datasheet, PDF (22/192 Pages) List of Unclassifed Manufacturers – 12O COMPATIBLE PCI BUS MASTER INTERFACE CHIP FOR ADAPTERS AND EMBEDDED SYSTEMS

SECTION 3
PCI 9080
Table 3-1. NB# and Serial EEPROM Guidelines
NB#
Low
High
Serial
EEPROM
No
Programmed
Blank
No
Programmed
Blank
System Boot Condition
Boot with PCI 9080 default values.
Boot with serial EEPROM values.
Not recommended (uses default
values).
Local processor programs PCI 9080
registers, then sets Local Init Status
(Table 4-59[31] = done).
Note: Some systems hang if Direct
Slave reads and writes take too long
(during initialization, the PCI host also
performs Direct Slave accesses). Value
of PCI Target Retry Delay Clocks
(Table 4-39[31:28]) may resolve this
problem.
Load serial EEPROM, but local
processor can reprogram PCI 9080.
Load serial EEPROM (default values),
but local processor can reprogram PCI
9080. System can boot.
Note: Serial EEPROM can be
programmed through PCI 9080 after
system boots in this condition.
3.2.1 Serial EEPROM Initialization
During serial EEPROM initialization, PCI 9080 response
to PCI target accesses is RETRY. During serial
EEPROM initialization, PCI 9080 response to a local
processor is to hold off READYo#.
3.2.2 Local Initialization
PCI 9080 issues a RETRY to all PCI accesses until the
"Local Init Done bit" in the Init Control Register is set.
"Init Done bit" is programmable through local bus
configuration accesses. If this bit is not going to be set
by a local processor, then NB# input should be tied low.
Holding NB# input low externally forces the Local Init
Done bit to 1.
PCI 9080 default values are used if a serial EEPROM is
not present and local Init Status bit is set to 1 by holding
the NB# input low or set by the local processor.
3.3 SERIAL EEPROM
After reset, PCI 9080 attempts to read the serial
EEPROM to determine its presence. An active low start
bit indicates the serial EEPROM is present (PCI 9080
supports 93CS46 (1K) or 93CS56 (2K), selectable by
way of the EESEL pin). (Refer to the manufacturer’s
data sheet for the particular serial EEPROM being
used.) The first word is then checked to verify the serial
FUNCTIONAL DESCRIPTION
EEPROM is programmed. If the first word (16 bit) is all
ones, a blank serial EEPROM PCI 9080 uses default
values instead.
The 5 V serial EEPROM clock (EESK, pin 173) is
derived from the PCI clock. PCI 9080 generates the
serial EEPROM clock by internally dividing the PCI clock
by 32.
The serial EEPROM can be read or programmed from
the PCI or local bus. Bits [27:24] of the Serial EEPROM
Control Register (refer to Table 4-59[27:24]) controls the
PCI 9080 pins that enable the reading or writing of serial
EEPROM data bits. (Refer to the manufacturer’s data
sheet for the particular serial EEPROM being used.)
PCI 9080 has three serial EEPROM load options:
• Short Load Mode—SHORT# input pin is pulled
down and PCI 9080 loads five Lwords from the
serial EEPROM
• Long Load Mode—SHORT# input pin is pulled up,
bit 25 of the Local Bus Region Descriptor Register
(LOC:98h) is set to 0, and PCI 9080 loads
17 Lwords from the serial EEPROM (refer to Table
4-39)
• Extra Long Load Mode—SHORT# input pin is
pulled up, bit 25 of the Local Bus Region Descriptor
Register (LOC:98h) is set to 1 during Long Load
from the serial EEPROM, and PCI 9080 loads
21 Lwords from the serial EEPROM (refer to Table
4-39)
3.3.1 Short Serial EEPROM Load
The registers listed in Table 3-2 are loaded from serial
EEPROM after reset is de-asserted if SHORT# pin is
low. The serial EEPROM is organized in words (16 bit).
PCI 9080 first loads MSW (Most Significant Word; bits
[31:16]), starting from the most significant bit (bit 31).
PCI 9080 then loads LSW (Least Significant Word; bits
[15:0]), starting again from the most significant bit (bit
15). Therefore, PCI 9080 loads Device ID, Vendor ID,
class code, and so forth. The five 32-bit words are stored
sequentially in the serial EEPROM.
©PLX Technology, Inc., 1997
Page 13
Version 1.02