Hi All,
Can't anyone clarify this new spec. about receivers for me
and what the intention is?
THanks
Nik
nikolai@avanticorp.com
Qestions:
*********
* 1 *
*********
1. What is a receiver? Is it
a) A part of output buffer which receives controlloing
signal (in other words, input of output type buffer).
In this case it can be extended to enable node
of 3-state and I/O buffers.
b) That part of Input buffer, which is looking into
a transmission line and receives signals from
some output type buffer through the transmission line.
I would expect the unswer should be b). However, the spec.
says:
===begin===
1) The following new keyword is defined, and is placed in the
specification just below the [Rising Waveform] and [Falling Waveform]
keyword descriptions
=== end ===
But Input buffer has no [Rising Waveform] or [Falling Waveform].
I/O buffer does have, but Input buffer does not have and
we have no place to place [Receiver Delay] keyword.
If the answer is a), then, hey, how we can apply ramp
signal to input of the output buffer, if we do not know
its impedance, Capacitance, etc. ??
*********
* 2 *
*********
2) Examples are confusing. The should give receiver delay.
What we have in example 1:
===begin===
[Receiver Delay]
Start_point = 0.8v
Slope = 1v/1ns
End_point TABLE
|variable typ min max
1.4 INF 7.0ns INF
1.5 INF 5.0ns INF
1.51 INF 3.0ns 10.0ns
1.53 7.0ns 0.0ns 7.0ns
1.55 2.0ns 0.0ns 1.0ns
1.6 0.0ns 0.0ns 0.0ns
1.7 0.0ns 0.0ns 0.0ns
2.0 0.0ns 0.0ns 0.0ns
2.1 0.1ns 0.1ns 0.1ns
2.5 -0.2ns -0.1ns -0.5ns
=== end ===
delay is about 1ns, ok
example 2:
===begin===
[Receiver Delay]
Start_point = 0.8v
End_point = 2.0v
Slope TABLE
|variable typ min max
0.05/1ns -1.0 -3.5 -1.0
0.25/1ns -0.75 -2.0 -0.05
0.50/1ns -0.01 -0.5 -0.0
0.60/1ns 0.0 0.25 0.0
0.75/1ns 0.0 0.0 0.0
1.00/1ns 0.0 0.0 0.0
2.00/1ns +0.5 +0.2 +1.0
=== end ===
is it a delay about 1s, or data are in Volts,
or Nano is missing, or what is it?
*********
* 3 *
*********
3) Some delays are negative. This is very very bad.
Should be always positive. Just from stand point of
causality. You apply a signal and then 1ns BEFORE that event
your receiver tells you the signal has arrived.
Simulators have to add some 'base' delay.
Simulator_A will add 1ns, Simulator_B will add 10ns, etc.
Why not IBIS spec add this 'base' delay and all have
less headahe?
*********
* 4 *
*********
4) Input buffer has Vinl, Vinh. If [Receiver Delay]-s
are specified, then Vinl, Vinh should be discarded. Right?
If ONLY 1 [Receiver Delay] is given, say for rising ramp,
then we still use Vinl, Vinh, right ?
Vinl, Vinh MUST be always given and BE CONSISTENT with
[Receiver Delay] if the last is given. Right?
*********
* end *
*********
----- Begin Included Message -----
Buffer Issue Resolution Document (BIRD)
BIRD ID#: 61
ISSUE TITLE: Enhanced Characterization of Receivers
REQUESTOR: D.C Sessions (Philips), Richard Mellitz, Stephen Peters,
Arpad Muranyi (Intel Corp)
DATE SUBMITTED: August 9, 1999
DATE ACCEPTED BY IBIS OPEN FORUM:
*******************************************************************************
*******************************************************************************
STATEMENT OF THE ISSUE: The current specification allows the user to
describe the static Vinh and Vinl thresholds of a receiver. However, these
parameters specify only the DC input thresholds at which the output of
a receiver switches state. They do not describe a digital logic receiver's
dynamic performance. Dynamic performance includes such items as how a
device's setup or hold time varies with input overdrive, or how a receiver
behaves when an input waveform rings back into the area between Vinh and
Vinl. In addition, the current specification does not support simulation
methodologies that rely on specifying the total delay from the input of an
output buffer to the output of the receiver. This bird offers a way for the
user to specify a receiver's propagation delay and dynamic characteristics in
enough detail so that a simulation tool can model a receiver's response to
any arbitrary waveform.
*******************************************************************************
STATEMENT OF THE RESOLVED SPECIFICATIONS:
1) The following new keyword is defined, and is placed in the
specification just below the [Rising Waveform] and [Falling Waveform]
keyword descriptions
|=============================================================================
| Keyword: [Receiver Delay]
| Required: No
| Sub-Params: Start_point, End_point, Slope
| Description: This keyword specifies how the propagation delay of an
| input receiver varies as a function of input overdrive or
| input waveform slope.
|
| Usage Rules: The [Receiver Delay] keyword is followed immediately by the
| three subparameter names and their arguments. The Start_point
| and End_point subparameters define the starting and ending
| voltage points of a linear ramp while the Slope parameter
| specifies the slope of that ramp. Slope is given in units of
| volts per second (V/S). All three subparameters are required.
|
| Subparameter Usage:
| The intent of the subparameters is to specify a set of linear
| ramps that vary only in starting point, ending point, or
| slope. Therefore, when assigning values to the subparameters,
| two of the three subparameters must be assigned fixed values,
| while the third subparameter uses as its argument the reserved
| word TABLE. The use of the word TABLE indicates that this
| subparameter is the independent variable in the associated
| receiver delay table. The subparameter that uses the TABLE
| argument must appear after the other two subparameters and
| before the receiver delay table.
|
| Numerical arguments are separated from their associated
| subparameter by an equals sign (=); white space around the
| equals sign is optional. The TABLE argument is separate
| from its associated subparameter by white space.
|
| Receiver Delay Table:
| Following the subparameters is the receiver delay table itself.
| This table consists of four columns. The first column lists
| either the starting voltage, ending voltage or slope of the
| linear ramp (i.e. the independent variable) as determined by
| the subparameter with the TABLE argument. The second thru
| fourth columns list the change in the receiver's propagation
| delay. This "change in delay" is relative to the receiver's
| delay when it is stimulated using the same overdrive and edge
| rate conditions used to specify the device's setup and hold
| times. The delay columns are arranged in the standard typ,
| min, max format. All four entries must be placed on the same
| line and must be separated by at least one white space. All
| four columns are required. However, data is required only for
| the typical column. If minimum or maximum data is not available
| use the reserved word NA. Each receiver delay table is limited
| to 100 rows and only one receiver delay table is allowed per
| [Receiver Delay] keyword. However, there are no restrictions
| on the number of [Receiver Delay] keywords per [Model] keyword.
| Note that the [Receiver Delay] keyword is not allowed unless
| the Model_type of the [Model] is one of the Input or I/O
| models types.
|
| Use of INF as a Receiver Delay:
| When building a receiver delay table the user may specify an
| input condition that does not result in the receiver's output
| changing state. In that case, the receiver delay is considered
| infinite, and the reserved word INF is used in the delay
| column. See the examples below.
|
| Other Notes:
| It is expected that the user will provide enough [Receiver
| Delay] keywords (i.e. characterization data) to allow a CAE
| tool to build a model of the input receiver. It is expected
| that at least four [Receiver Delay] keywords will be required;
| two low to high going ramps and two high to low going ramps.
| However, the exact number of ramps and there content is up
| to the user and recommendations provided by the various
| simulation vendors.
|
| An example table showing how receiver delay varies vs. overdrive.
| Note the use of the reserved word INF.
|
[Receiver Delay]
Start_point = 0.8v
Slope = 1v/1ns
End_point TABLE
|variable typ min max
1.4 INF 7.0ns INF
1.5 INF 5.0ns INF
1.51 INF 3.0ns 10.0ns
1.53 7.0ns 0.0ns 7.0ns
1.55 2.0ns 0.0ns 1.0ns
1.6 0.0ns 0.0ns 0.0ns
1.7 0.0ns 0.0ns 0.0ns
2.0 0.0ns 0.0ns 0.0ns
2.1 0.1ns 0.1ns 0.1ns
2.5 -0.2ns -0.1ns -0.5ns
|
| A second table that characterizes receiver delay vs. the slope of the
| input waveform.
|
[Receiver Delay]
Start_point = 0.8v
End_point = 2.0v
Slope TABLE
|variable typ min max
0.05/1ns -1.0 -3.5 -1.0
0.25/1ns -0.75 -2.0 -0.05
0.50/1ns -0.01 -0.5 -0.0
0.60/1ns 0.0 0.25 0.0
0.75/1ns 0.0 0.0 0.0
1.00/1ns 0.0 0.0 0.0
2.00/1ns +0.5 +0.2 +1.0
|
|
|2) Item 2 under General Syntax Rules and Guidelines is modified to include
|the following reserved words
INF - used when a data value is so large it is considered infinite
TABLE - used to indicate that a subparameter's value(s) are part of a
table.
*******************************************************************************
ANALYSIS PATH/DATA THAT LED TO SPECIFICATION: This bird originated from
discussions held at the January '99 IBIS summit regarding the lack of a
way to accurately and realistically specify the input thresholds and
dynamic performance of a digital logic receiver. At the mid year '99 IBIS
summit D.C. Sessions, Stephen Peters, Richard Mellitz and Arpad Muranyi
agreed to meet to hammer out a proposal. This bird is one of the results.
The technical basis of this bird derives from simulation work done by
Richard Mellitz.
*******************************************************************************
ANY OTHER BACKGROUND INFORMATION:
*******************************************************************************
----- End Included Message -----
Received on Wed Aug 11 11:00:04 1999
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