PENTIUM® PROCESSOR (610\75)
Symbol
CLK
D/C#
D63-D0
DP7-DP0
[DPEN#]
PICD0
EADS#
EWBE#
FERR#
Type
I
O
I/O
I/O
I/O
I
I
O
Table 3. Quick Pin Reference (Contd.)
Name and Function
The clock input provides the fundamental timing for the Pentium processor
(610\75). Its frequency is the operating frequency of the Pentium processor
(610\75) external bus and requires TTL levels. All external timing parameters
except TDI, TDO, TMS, TRST#, and PICD0-1 are specified with respect to the
rising edge of CLK.
The data/code output is one of the primary bus cycle definition pins. It is driven
valid in the same clock as the ADS# signal is asserted. D/C# distinguishes
between data and code or special cycles.
These are the 64 data lines for the processor. Lines D7-D0 define the least
significant byte of the data bus; lines D63-D56 define the most significant byte
of the data bus. When the CPU is driving the data lines, they are driven during
the T2, T12, or T2P clocks for that cycle. During reads, the CPU samples the
data bus when BRDY# is returned.
These are the data parity pins for the processor. There is one for each byte of
the data bus. They are driven by the Pentium processor (610\75) with even
parity information on writes in the same clock as write data. Even parity
information must be driven back to the Pentium processor (610\75) on these
pins in the same clock as the data to ensure that the correct parity check status
is indicated by the Pentium processor (610\75) . DP7 applies to D63-D56; DP0
applies to D7-D0.
Dual processing enable is an output of the Dual processor and an input of the
Primary processor. The Dual processor drives DPEN# low to the Primary
processor at RESET to indicate that the Primary processor should enable dual
processor mode. Since the dual processing feature is not supported on the
Pentium processor (610\75) TCP package, DPEN# should never be asserted
(low) at RESET. DPEN# shares a pin with PICD0.
This signal indicates that a valid external address has been driven onto the
Pentium processor (610\75) address pins to be used for an inquire cycle.
The external write buffer empty input, when inactive (high), indicates that a
write cycle is pending in the external system. When the Pentium processor
(610\75) generates a write, and EWBE# is sampled inactive, the Pentium
processor (610\75) will hold off all subsequent writes to all E- or M-state lines in
the data cache until all write cycles have completed, as indicated by EWBE#
being active.
The floating point error pin is driven active when an unmasked floating point
error occurs. FERR# is similar to the ERROR# pin on the Intel387™ math
coprocessor. FERR# is included for compatibility with systems using DOS-type
floating point error reporting.
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