Asynchronous Vs. Synchronous For System Bus Signals; System Bus Frequency Select Signal (Bsel[1:0]); Test Access Port (Tap) Connection; Maximum Ratings - Intel CELERON 1.10 GHZ Datasheet

2.7.1

Asynchronous Vs. Synchronous for System Bus Signals

All AGTL+ signals are synchronous to BCLK. All of the CMOS, APIC, and TAP signals can be
applied asynchronously to BCLK. All APIC signals are synchronous to PICCLK. All TAP signals
are synchronous to TCK.
2.7.2

System Bus Frequency Select Signal (BSEL[1:0])

The BSEL pins have two functions. First, they can act as outputs and can be used by an external
clock generator to select the proper system bus frequency. Second, they can act as an inputs and
can be used by a system BIOS to detect and report the processor core frequency. See the Intel
®
Celeron
an example implementation of BSEL.
BSEL0 is 3.3 V tolerant for the S.E.P. Package, while it is 2.5 V tolerant on the PPGA package. A
logic-low on BSEL0 is defined as 66 MHz. On the FC-PGA/FC-PGA2 packages a logic low on
both BSEL0 and BSEL1 are defined as 66 MHz and are 3.3V tolerant.
2.8

Test Access Port (TAP) Connection

Due to the voltage levels supported by other components in the Test Access Port (TAP) logic, it is
recommended that the Celeron processor be first in the TAP chain and followed by any other
components within the system. A translation buffer should be used to connect to the rest of the
chain unless one of the other components is capable of accepting a Vcc
Similar considerations must be made for TCK, TMS, and TRST#. Two copies of each signal may
be required with each driving a different voltage level.
A Debug Port may be placed at the start and end of the TAP chain with the TDI of the first
component coming from the Debug Port and the TDO from the last component going to the Debug
Port.
2.9

Maximum Ratings

Table 4 contains the Celeron processor stress ratings only. Functional operation at the absolute
maximum and minimum is not implied nor guaranteed. The processor should not receive a clock
while subjected to these conditions. Functional operating conditions are given in the AC and DC
tables. Extended exposure to the maximum ratings may affect device reliability. Furthermore,
although the processor contains protective circuitry to resist damage from static electric discharge,
one should always take precautions to avoid high static voltages or electric fields.
Datasheet
®
Processor with the Intel
®
Intel Celeron
440ZX-66 AGPset Design Guide (Order Number 245126) for
®
Processor up to 1.10 GHz
(1.5V or 2.5 V) input.
CMOS
®
23