.......................Document #: 001-05103 Rev *B Page 3 of 27
Frequency Select Pins (FSA, FSB, and FSC)
Host clock frequency selection is achieved by applying the
appropriate logic levels to FSA, FSB, FSC inputs prior to
CK_PWRGD assertion (as seen by the clock synthesizer).
Upon CK_PWRGD being sampled HIGH by the clock chip
(indicating processor CK_PWRGD voltage is stable), the clock
chip samples the FSA, FSB, and FSC input values. For all
logic levels of FSA, FSB, and FSC, CK_PWRGD employs a
one-shot functionality in that once a valid HIGH on
CK_PWRGD has been sampled, all further CK_PWRGD,
FSA, FSB, and FSC transitions will be ignored, except in test
mode.
Serial Data Interface
To enhance the flexibility and function of the clock synthesizer,
a two-signal serial interface is provided. Through the Serial
Data Interface, various device functions, such as individual
clock output buffers, can be individually enabled or disabled.
The registers associated with the Serial Data Interface
initialize to their default setting upon power-up, and therefore
use of this interface is optional. Clock device register changes
are normally made upon system initialization, if any are
required. The interface cannot be used during system
operation for power management functions.
32 PCI2/TME I/O, PU,
SE
33-MHz clock output/Trusted Mode Enable Strap
Strap at pin 39 assertion to determine if the part is in trusted mode or not.
Internal pull-up resistor of 100K to 3.3V, use 10K resistor to pull it low externally
if needed
0 = Normal mode
1= Trusted mode (default)
33 PCI3 O, SE 33MHz clock output / 3.3V-tolerant input select pin to select termination scheme
for differential clocks.
34 PCI4/FCTSEL1 I/O, PD 33-MHz clock output/3.3V LVTTL input for selecting pins 47,48 (SRC[T/C]0,
100M[T/C]) and pins 43,44 (DOT96[T/C] and 27M Spread and Non-spread)
(sampled on pin 39 assertion).
Internal pull-down resistor of 100K to GND
37 ITP_SEL/PCIF0 I/O, PD,
SE
3.3V LVTTL input to enable SRC10 or CPU2_ITP/33-MHz clock output. (sampled
on pin 39 assertion).
Internal pull-down resistor of 100K to GND
1 = CPU2_ITP, 0 = SRC10
39 CKPWRGD/PD# I 3.3V LVTTL input. This pin is a level sensitive strobe. When asserted, it latches
data on the FSA, FSB, FSC, FCTSEL1 and ITP_SEL pins. After assertion, it
becomes a real time input for controlling power down.
40 VDD_48 PWR 3.3V power supply for outputs.
41 48M/FSA I/O Fixed 48-MHz clock output/3.3V-tolerant input for CPU frequency selection
Refer to DC Electrical Specifications table for Vil_FS and Vih_FS specifications.
42 VSS_48 GND Ground for outputs.
43, 44 DOT96T/ 27M_NSS
DOT96C/ 27M_SS
O, DIF Fixed 96-MHz clock output or 27 Mhz Spread and Non-spread output Selected
via FCTSEL1 at pin 39 assertion.
45 FSB/TEST_MODE I 3.3V-tolerant input for CPU frequency selection. Selects Ref/N or Tri-state when
in test mode
0 = Tri-state, 1 = Ref/N
Refer to DC Electrical Specifications table for Vil_FS and Vih_FS specifications.
47, 48 SRC[T/C]0/
LCD100M[T/C]
O,DIF 100-MHz differential serial reference clock output/Differential 96/100-MHz SS
clock for flat-panel display
Selected via FCTSEL1 at pin 39 assertion.
50, 51 SRCT_1/SATAT,
SRCC_1/SATAC
O, DIF 100-MHz Differential serial reference clocks.
Pin Description (continued)
Pin No. Name Type Description
FCTSEL1 Pin 43 Pin 44 Pin 47 Pin 48
0 DOT96T DOT96C 96/100M_T 96/100M_C
1 27M_NSS 27M_SS SRCT0 SRCC0
