
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.
Содержание Pentium Pro Family
Страница 17: ...1 Component Introduction ...
Страница 26: ...2 Pentium Pro Processor Architecture Overview ...
Страница 27: ......
Страница 36: ...3 Bus Overview ...
Страница 62: ...4 Bus Protocol ...
Страница 105: ...5 Bus Transactions and Operations ...
Страница 126: ...6 Range Registers ...
Страница 131: ...7 Cache Protocol ...
Страница 135: ...8 Data Integrity ...
Страница 148: ...9 Configuration ...
Страница 161: ...10 Pentium Pro Processor Test Access Port TAP ...
Страница 172: ...11 Electrical Specifications ...
Страница 201: ...12 GTL Interface Specification ...
Страница 229: ...13 3 3V Tolerant Signal Quality Specifications ...
Страница 233: ...14 Thermal Specifications ...
Страница 239: ...15 Mechanical Specifications ...
Страница 241: ...15 2 MECHANICAL SPECIFICATIONS s Figure 15 1 Package Dimensions Bottom View ...
Страница 252: ...16 Tools ...
Страница 260: ...16 8 TOOLS Figure 16 4 Generic MP System Layout for Debug Port Connection ...
Страница 264: ...17 OverDrive Processor Socket Specification ...
Страница 290: ...A Signals Reference ...
Страница 320: ...Index ...
Страница 328: ......