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What is "Vcd2Apf - Description Tool"?

The Vcd2Apf program is a tool to convert the RTL simulation resultant files into the files of simulation patterns in Epson-specific format, called APF. The generated APF files are used for netlist simulation.

To implement the Vcd2apf file conversion, follow the flow shown below.

In this description, VCD is the data file that the time and the value of each signal switch is recorded, whereas APF is the simulation pattern file that the input and output signal values are written in one line every single cycle. Therefore, Vcd2apf is a software that converts signal switch information to signal values in units of cycle.

" Vcd2apf"-start up is explained in "Vcd2apf start up guide".This guide explains enough for Vcd2apf operation.For further information,please refer to" Vcd2Apf -Appendix".

RTL simulation
Dump the signals which will be ASIC I/O pins and the output enable signals for bi-directional I/O pins in the VCD format file. If the file contains other data, it might have slowed down the simulation processing, but it cause no serious problems.
However, all the signals need to be included in one module.
Use Vcd2apf to analyze VCD
Start Vcd2apf (refer to Vcd2apf start up guide ) and analyze the VCD file. Take the following steps and the analysis results will be shown in the table.
  • Click the "Select" button of the "Input VCD file"" and select the VCD file.
  • Click the "Select" button of the "Top module instance" and select the top module instance name. The term "top module" here, means the module that contains the signals which will be ASIC I/O pins and the output enable signals for bi-directional I/O pins.
  • Enter in the "VCD cycle time" the value in the RTL simulation .
  • Enter the strobe time in the RTL simulation in the "Strobe". The value sampled at the time entered "Strobe" will be the expected value of netlist simulation.
  • Click the "VCD analysis" button, and the VCD will be analyzed and the result will be shown in the table below.
    The VCD analysis results are shown from the first item to the third,"number of occurances on the table. And, the "number of occurrences" are the aggregate results of remainder obtained by dividing the change time of each signal in the "VCD cycle time", namely, the change time in each cycle. However, if there is a change other than 0ns within the cycle, the first 0ns is ignored. The items right from the "IOB" , is to input the data for the APF file generation. Because VCD does not include I/O information, the "IOB" column turns red (error message) to prompt the user to input the I/O information at first when the VCD analysis is completed.
Modify the table
When data appears in the table, input each signal data to generate APF. Basically, enter the data necessary to generate APF in the right-hand items starting from the "IOB" , referring to the data shown from the first item to the third, number of occurances, "which is the VCD analysis result. The cells need to be filled in or modified are shown in red. Add or modify the information until all red cells disappear. The yellow cells indicate warnings. They do not mean error and do not neet to be modified, but please ensure that they have no problems.
The descriptions of errors and warnings are given in the "Comment".
Placing the mouse pointer over the red or yellow cell,
the description of the relevant error or warning pops up. Similarly, placing the
mouse pointer over the items line of the table, the short description of the
column pops up.
  • It is possible to make the same modifications to multiple lines of the table at one time, Select the multiple lines first. The multiple lines,- can be selected by draging the mouse over the lines, or clicking the mouse while pressing the "Shift" key (area selection) or the "Ctrl" key (individual cell selectionl). Here, inputs and modifications are applied to all the lines of the selected column (light blue); and thus care must be taken to select the right column.
  • To delete unnecessary signals, select the line and click the "cut" button. To make the table ( the APF file , too ) easy to read, the user can sort the line and the signal in order by the "Cut" and "Paste" buttons, or insert blank lines (blank columns in the APF file) by pressing the "Insert" button.
  • To add test and other pins, insert blank lines first by "Insert" and then input "IOB" or "APF pin". Also add "Delay*" or "Output En" if needed, and enter that signal value to the "x" column, even if the signal is input or output. Only one signal value is allowed for one pattern.
  • Input the following I/O attributes in the column "IOB": I for input; P for positive pulse input; N for negative pulse input; O for output; B for bi-directional; Bo for bi-directional output and Bi for bi-directional input. The term of "B" here is the attribute when the bi-directional I/O is descrided by one pin is described for the bi-directional I/O pin, "Bi" and "Bo" are the attributes to describe the signals separately which will be bi-directional I/O are decomposed to input and output signals. Specify "Bi" and "Bo" in series with "Bo" first and "Bi" in the line immediately below.
  • The column "APF pin" is provided to change pin names when the original pin names ("VCD pin") do not meet the APF rules. Same character strings as the "VCD pin" are input in advance, and modify them as needed. If an asterisk (*) is input at the end of the above "VDC pin" name , the square brackets automatically disappear and lowercase characters are changed into uppercase characters. For example, if "*" is input at the end of "out[1]", it is changed to "OUT1" automatically.
  • In the columns "Delay 1" and "Delay 2",enter the time to sample the input signal as needed. If only one delay value exists in the VCD analysis result (two delay values in the case of "P" and "N"), the value is automatically input when the "IOB" column is input. If "=min" is input, the minimum delay value is shown. If "=max" is input, the maximum delay value is shown. If "=1" is input, the most frequent delay value is copied, if "=2", the second most frequent value, and if "=3", the third most frequent value. When desired to input the maximum delay value in multiple lines, for example, select the multiple lines in the "Delay 1" column, and input "=max" once. The "min" and "max" are case insensitive here.
  • In the "Output En" column,enter the output enable signal names for bi-directional pins. Here, if the signal enters the output state when it goes 0 (zero), add an exclamation mark (!) before the signal name.
  • In the "x" and "z" columns, enter the value to which the input signal should be converted, in case either x or z appears as the input value. The entries to these columns are not mandatory; enter them as needed. When these columns are filled in for output signals ("O" and "Bo"), the x and z of the output signals are converted into the filled values. However, in the case of bi-directional signals ("B"), they are converted to the values in the "x" and "z" columns only when the signals are in the input state. Bi-directional signals ("B") in the output state are not converted. This function is used to change the inputs of x and z, which are prohibited in APF, to 0 and 1.
  • In the "0" and "1" columns, enter the value to which the output signal should be converted, in case either 0 or 1 appears as the output value. These entries are not mandatory; enter them as needed. When these columns are filled in for input signals ("I", "P", "N", and "Bi"), the input 0 and 1 are converted into the filled values. However, in the case of bi-directional signals ("B"), they are converted to the values in the "0" and "1" columns only when the signals are in the output state. Bi-directional signals ("B") in the input state are not converted. This function is typically used to change the value of open-drain output pin from 1 to Z.
  • The "Read" button to the right of "Template" reads the modifications made to the table and saved previously. When making the same modifications to multiple VCD files, make modifications to a VCD file and save the table data as a template. Then the same modifications will be made to other files simply by pressing the "Read" button.
  • The "Save" button saves the table data as a template.
  • By activating the "Horizontal Scroll" button, the table width remains unchanged regardless of the browser width and the table can be horizontally scrolled. Clicking the "R" button resets the table to the default width.
  • To change the order of column titles, drag a title and drop it at the desired position. To change the column width, drag the right side border line of each title column.
When all errors disappear, save the table as a template, and send it (CSV file) together with the VCD file to Epson. Also please inform our responsible designer about the cycle time and strobe timing in the VCD and APF files. The subsequent tasks will be taken care of by Seiko Epson. If any problem occurs in those tasks, Epson will discuss it with the customer to figure out possible solutions.
Generate APF file
When all errors disappear, enter the "APF Cycle Time", "Strobe" and "Delay multiple". Then, click the "Generate APF" button. Clicking the button opens the APF file selection window. For the file selection, select the folder to save the APF file, enter the APF file name, and click the "OK" button to generate the APF file.
The "APF Cycle Time" and "Strobe" are not used in the VCD to APF conversion; they are only transcribed to the APF file. "Delay 1" and "Delay 2" in the table are respectively multiplied by the "Delay multiple", and the multiplied values are defined as the delays of input pins in the APF file. Acceptable delay values are zero and positive integers. To adjust delay values, edit the generated APF file.
Update APF file
To match the "$DESIGN" and "$IOCONT" section data in the generated APF file with those in the netlists, update the APF file by running "apf2apf".
The "apf2apf", a utility of "EPITS" and "EPITS7", updates the APF file by the command line like the example shown below:
example) apf2apf ..\func1.apf -r rpt\TOP.rpt -u rpt\TOP.tpl -o pattern\func1.apf
where the first ".apf" file is the APF file generated by Vcd2apf, the ".rpt" and the ".tpl" files are generated by SNRC, the design rule checker of Seiko Epson, and the last ".apf" file is the updated APF file to output.
Check APF file
Check the APF file by running "apfcheck".
The "apfcheck" is a utility of "EPITS" and "EPITS7". For usage, refer to the respective user's manuals for "EPITS" and "EPITS7".

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