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BIRD ID#: 130
ISSUE TITLE: Crosstalk Clarification With Respect to AMI
REQUESTOR: Ken Willis, Sigrity, Inc.
Arpad Muranyi, Mentor Graphics, Inc.
DATE SUBMITTED: April 12, 2011
DATE REVISED:
DATE ACCEPTED BY IBIS OPEN FORUM: June 24, 2011
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STATEMENT OF THE ISSUE:
The description of how crosstalk is to be handled with respect to AMI models
is unclear in the 5.0 version of the IBIS spec.
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STATEMENT OF THE RESOLVED SPECIFICATIONS:
On pg. 6, 180, and 185 change the section title for section 3.1.2.2
to "number_of_rows" from "row_size".
On pg. 185, in section 3.1.1 replace these lines:
| long AMI_Init (double *impulse_matrix,
| long row_size,
with the following lines:
| long AMI_Init (double *impulse_matrix,
|* long number_of_rows,
Replace the following text in Section 3.1.2.1:
| 3.1.2.1 impulse_matrix
| ======================
|
| 'impulse_matrix' is the channel impulse response matrix. The impulse values
| are in volts and are uniformly spaced in time. The sample spacing is given
| by the parameter 'sample_interval'.
|
| The impulse_matrix is stored in a single dimensional array of floating point
| numbers which is formed by concatenating the columns of the impulse response
| matrix, starting with the first column and ending with the last column. The
| matrix elements can be retrieved/identified using
|
| impulse_matrix[idx] = element (row, col)
| idx = col * number_of_rows + row
| row - row index , ranges from 0 to row_size-1
| col - column index, ranges from 0 to aggressors
|
| The first column of the impulse_matrix is the impulse response for the
| primary channel. The rest are the impulse responses from aggressor drivers
| to the victim receiver.
|
| The AMI_Init function may return a modified impulse response by modifying
| the first column of impulse_matrix. If the impulse response is modified,
| the new impulse response is expected to represent the filtered response.
| The number of items in the matrix should remain unchanged.
|
| The aggressor columns of the matrix should not be modified.
With the following text:
| 3.1.2.1 impulse_matrix
| ======================
|
|* 'impulse_matrix' points to a memory location where the collection of
|* channel voltage impulse responses, called the "impulse response matrix",
|* is stored in the form of a single dimensional array of floating point
|* numbers. The impulse response values are uniformly spaced in time.
|* The sample spacing is given by the parameter 'sample_interval'.
|*
|* The first column of the impulse response matrix is the impulse response
|* for a through channel, a channel that serves as a communication path
|* between a transmitter/receiver pair. The rest of the columns contain the
|* impulse responses of crosstalk channels. Crosstalk channels describe
|* the paths between aggressor transmitters and victim receiver(s).
|* Transmitters which are not part of a through channel between a certain
|* transmitter/receiver pair are all considered aggressor transmitters with
|* respect to that through channel. The receiver of the through channel in
|* consideration is referred to as the victim receiver. The crosstalk
|* impulse responses may be placed into the impulse response matrix in any
|* order.
|*
|* The single dimensional array of 'impulse_matrix' is formed by concatenating
|* the columns of an impulse response matrix, starting with the first column
|* and ending with the last column. The matrix elements can be retrieved or
|* identified using the following relationships:
|
| impulse_matrix[idx] = impulse response matrix element (row, col)
|* idx = col * number_of_rows + row
|* row: row index ranges from 0 to number_of_rows-1
|* col: column index ranges from 0 to aggressors
|*
|* Each impulse response in the impulse response matrix must have the same
|* sample spacing and the same length.
|*
|* To include any crosstalk effects in the Reference Flows described in
|* this section of this specification, the crosstalk impulse responses
|* must be included in the 'impulse_matrix' and passed to the transmitter and
|* receiver AMI_Init functions. If present, any filtering in the transmitter
|* and/or receiver AMI_Init function(s) must also be applied to the crosstalk
|* impulse responses to properly account for the crosstalk effects.
|*
|* Note that the 'impulse_matrix' will contain a different set of crosstalk
|* impulse responses for the transmitter and receiver AMI_Init calls, even for
|* a transmitter/receiver pair of the same through channel. A transmitter's
|* AMI_Init function operates on those impulse responses which originate from
|* that transmitter, including the through channel and crosstalk channel
|* impulse responses. A victim receiver's AMI_Init function, on the other
|* hand, operates on all of those impulse responses which are received by
|* that victim receiver, including the through channel and crosstalk channel
|* impulse responses.
|*
|* As an illustration, consider a crosstalk analysis with five channels
|* numbered 1 through 5, where channel 3 in the center is the through
|* channel of the transmitter/receiver pair Tx3/Rx3, and Rx3 is the
|* victim receiver. In this case channels 1, 2 and 4, 5 are the aggressor
|* channels with the aggressor transmitters Tx1, Tx2, Tx4 and Tx5. If the
|* five 'impulse_matrix'-es of the five transmitters' AMI_Init functions
|* contain the following data:
|*
|*************************************
|* impulse_matrix impulse_matrix
|* column 1 column 2
|*
|*Tx1 IR1_1 IR1_3
|*Tx2 IR2_2 IR2_3
|*Tx3 IR3_3
|*Tx4 IR4_4 IR4_3
|*Tx5 IR5_5 IR5_3
|*************************************
|*
|* then the 'impulse_matrix' passed into the victim receiver's (Rx3) AMI_Init
|* function will contain the following data:
|*
|*********************************************************************************
|* impulse_matrix impulse_matrix impulse_matrix impulse_matrix impulse_matrix
|* column 1 column 2 column 3 column 4 column 5
|*
|*Rx3 Tx3Init(IR3_3) Tx1Init(IR1_3) Tx2Init(IR2_3) Tx4Init(IR4_3) Tx5Init(IR5_3)
|*********************************************************************************
|*
|* where "IRi_j" represents the impulse response from the transmitter on
|* channel i to the receiver on channel j, Tx1Init() .. Tx5Init() represents
|* the output of a transmitter's AMI_Init function which modified the impulse
|* response denoted inside the parentheses. Note that while in this example
|* the 'impulse_matrix' of each transmitter's AMI_Init function contains at
|* most one crosstalk impulse response, the victim receiver's 'impulse_matrix'
|* contains four crosstalk impulse responses. Also, using the above notation
|* note that the first index number of each impulse response passed to the
|* transmitter's AMI_Init function matches the transmitter's channel number,
|* and the second index number of each impulse response passed to the
|* receiver's AMI_Init function matches the receiver's channel number.
|*
|* It is the EDA tool's responsibility to rearrange the content of the
|* 'impulse_matrix' between the transmitter and receiver AMI_Init calls.
|*
|* The EDA tool is also responsible to limit the number of crosstalk channel
|* impulse responses in 'impulse_matrix' so that they shall not exceed
|* 'Max_Init_Aggressors' as specified in the corresponding .ami parameter
|* file of the algorithmic model. Consequently, the 'aggressors' parameter
|* of the AMI_Init function shall never contain a greater value than the
|* value provided in 'Max_Init_Aggressors' of the corresponding .ami parameter
|* file. While the allocated memory space for 'impulse_matrix' may be larger,
|* it is assumed that there is no meaningful data in that space beyond the
|* last column of the impulse response matrix that is stored in it.
|*
|* The AMI_Init function must not change the size or organization of
|* 'impulse_matrix' that it was given in any way.
|*
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ANALYSIS PATH/DATA THAT LED TO SPECIFICATION:
Discussion within the IBIS-ATM committee provided many important inputs to
this BIRD. It was desirable to clarify that the impulse_matrix columns
populated by the aggressor channels should include any impulse response
modification that is to be made by the respective aggressor transmitters.
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ANY OTHER BACKGROUND INFORMATION:
The following documents are provided as supporting material for this BIRD:
- "CrossTalk_IRmatrix_02.pdf", provided by Arpad Muranyi of Mentor Graphics
http://www.vhdl.org/pub/ibis/macromodel_wip/archive/20110331/arpadmuranyi/impulse_matrix%20and%20cross%20talk%20in%20IBIS-AMI/CrossTalk_IRmatrix_02.pdf
- "CrossTalk.pdf", provided by Walter Katz of SiSoft
http://www.vhdl.org/pub/ibis/macromodel_wip/archive/20110308/walterkatz/Impulse%20Crosstalk%20Matrix%20Explanation%20Using%20Touchstone%20Example/Crosstalk.pdf
The BIRD was unanimously approved at the June 24, 2011 IBIS IOpen Forum teleconference.
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