
12-17
GTL+ INTERFACE SPECIFICATION
T
HD
’ is the receiver’s hold time plus board clock driver and clock distribution skew minus the
driver’s on-chip clock phase shift, clock distribution skew, and jitter, plus other data latch or
JTAG delays (assuming these driver numbers are not included in the driver circuit simulation, as
was done for setup in the above paragraph). Note that T
HD
’ may end up being a negative number,
i.e. ahead of the clock, rather than after it. That would be acceptable, since that is equivalent to
shifting the driver output later in time had these extra delays been added to the driver as opposed
to setup and hold.
When using Ref8N to validate a driver design, it is recommended that all relevant combinations
of driver and receiver locations be checked.
As with other buffer technologies, such as TTL or CMOS, any given buffer design is not guar-
anteed to always meet the requirements of all possible system and network topologies. Meeting
the acceptance criteria listed in this document helps ensure the I/O buffer can be used in a variety
of GTL+ applications, but it is the system designer’s responsibility to examine the performance
of the buffer in the specific application to ensure that all GTL+ networks meet the signal quality
requirements.
12.2.3.
Determining Clock-To-Out, Setup and Hold
This section describes how to determine setup, hold and clock to out timings.
12.2.3.1.
CLOCK-TO-OUTPUT TIME, T
CO
T
CO
is measured using the test load in Figure 12-11, and is the delay from the 1.5 V crossing
point of the clock signal at the clock input pin of the device, to the V
REF
crossing point of the
output signal at the output pin of the device. For simulation purposes, the test load can be re-
placed by its electrical equivalent, which is a single 25
Ω
resistor connected directly to the pack-
age pin and terminated to 1.5V.
In a production test environment, it is nearly impossible to measure T
CO
directly at the output
pin of the device, instead, the test is performed a finite distance away from the pin and compen-
sated for the finite distance. The test load circuit shown in Figure 12-11 takes this into account
by making this finite distance a 50-
Ω
transmission line. To get the exact timings at the output
pin, the propagation delay along the transmission line must be subtracted from the measured val-
ue at the probe point.
Summary of Contents for Pentium Pro Family
Page 17: ...1 Component Introduction ...
Page 26: ...2 Pentium Pro Processor Architecture Overview ...
Page 27: ......
Page 36: ...3 Bus Overview ...
Page 62: ...4 Bus Protocol ...
Page 105: ...5 Bus Transactions and Operations ...
Page 126: ...6 Range Registers ...
Page 131: ...7 Cache Protocol ...
Page 135: ...8 Data Integrity ...
Page 148: ...9 Configuration ...
Page 161: ...10 Pentium Pro Processor Test Access Port TAP ...
Page 172: ...11 Electrical Specifications ...
Page 201: ...12 GTL Interface Specification ...
Page 229: ...13 3 3V Tolerant Signal Quality Specifications ...
Page 233: ...14 Thermal Specifications ...
Page 239: ...15 Mechanical Specifications ...
Page 241: ...15 2 MECHANICAL SPECIFICATIONS s Figure 15 1 Package Dimensions Bottom View ...
Page 252: ...16 Tools ...
Page 260: ...16 8 TOOLS Figure 16 4 Generic MP System Layout for Debug Port Connection ...
Page 264: ...17 OverDrive Processor Socket Specification ...
Page 290: ...A Signals Reference ...
Page 320: ...Index ...
Page 328: ......