Intel
®
81341 and 81342 I/O Processors
December 2007
Developer’s Manual
Order Number: 315037-002US
987
Clocking and Reset—Intel
®
81341 and 81342
19.1.1.2.1 Central Resource Mode (PCIX_EP# = ‘1’)
When operating as the Central Resource (
PCIX_EP#
= 1), the bus PCI bus operating
frequency and default value in ATUX PCSR[19:16] is determined based on the sampling
of
PCIXCAP
,
P_MODE2
,
M66EN
,
PCIXM1_100#
, and
PCIXM2_100#
.
When PCI Express* REFCLK is the primary clock source, the
CR_FREQ[1:0]
pins can
be used to control the operating frequency of an external clock source for the PCI bus.
The
CR_FREQ[1:0]
value can be changed by setting bits[19:16] in the ATUX PCSR
register (offset x074).
Table 625. PCI Bus Frequency Initialization
a
a. 81341 and 81342 does not support PCI-X 533Mhz.
P_PCIXCAP P_MODE2 P_M66EN PCIXM1_100
#
PCIXM2_100
#
PCI Bus Mode PCI Bus Frequency
ATUX
PCSR[19:16
]
< 0.11VCC
–
b
b. A ‘–’ in table indicates value is a ‘don’t care’ for computing bus mode/frequency. All signals must still be pulled to a valid logic
level.
Ground –
–
PCI
33 MHz
1111
< 0.11VCC
–
Not
connected
–
–
PCI
66 MHz
1111
< 0.6VCC &
> 0.11 VCC
GND
–
–
–
PCI-X
Mode 1
66 MHz
1110
< 0.6VCC &
> 0.11VCC
VCC
–
–
GND
PCI-X
Mode 2
100 MHz
(PCI-X 200 MHz)
0101
< 0.6VCC &
> 0.11VCC
VCC
–
–
VCC
PCI-X
Mode 2
133 MHz
(PCI-X 266 MHz)
0100
< 0.89VCC &
> 0.6VCC
–
–
–
–
PCI-X
Mode 1
66 MHz
1110
> 0.89VCC
–
–
GND
–
PCI-X
Mode 1
100 MHz
1101
> 0.89VCC
–
–
VCC
–
PCI-X
Mode 1
133 MHz
1100
Table 626. CR_FREQ[1:0] Encoding
ATUX PCSR[19:16] (PCIX Init
Pattern)
ATUX PCSR[10]
(P_M66EN)
CR_FREQ[1:0
]
Bus Frequency
Bus Mode
1111
0
11
33 MHz
Conventional PCI
1111
1
10
66 MHz
Conventional PCI
1110
–
10
66 MHz
PCI-X
1101
–
01
100 MHz
PCI-X
1100
–
00
133 MHz
PCI-X