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Overview:Overview:

IntroductionIntroduction

SVF structureSVF structure

SVF commandsSVF commands

SVF TAP state name used for eachSVF TAP state name used for each

IEEE 1149.1 TAP state name.IEEE 1149.1 TAP state name.

An example of SVF fileAn example of SVF file

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Introduction:Introduction:

The original SVF was developed jointly by The original SVF was developed jointly by Texas Instruments and Teradyne in 1991.Texas Instruments and Teradyne in 1991.

The need for SVF arose from the desire to The need for SVF arose from the desire to have vendor-independent IEEE 1149.1 test have vendor-independent IEEE 1149.1 test patterns that are transportable across a patterns that are transportable across a wide selection of simulation software and wide selection of simulation software and test equipment -- from design verification test equipment -- from design verification through field diagnostics. through field diagnostics.

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SVF is a standard ASCII format for SVF is a standard ASCII format for expressing test patterns that represent the expressing test patterns that represent the stimulus, expected response, and mask stimulus, expected response, and mask data for IEEE 1149.1-based tests. data for IEEE 1149.1-based tests.

The underlying models of SVF format The underlying models of SVF format assume that all operations begin and end assume that all operations begin and end in stable state.in stable state.

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SVF has proven itself to be a useful and SVF has proven itself to be a useful and reliable format for exchanging data reliable format for exchanging data between the Boundary Scan TAP and the between the Boundary Scan TAP and the software that drives it. software that drives it.

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SVF Structure:SVF Structure:

An SVF file contains a set of ASCII An SVF file contains a set of ASCII statements. statements.

The maximum number of characters The maximum number of characters allowed on a line is 256.allowed on a line is 256.

One SVF statement can span more than One SVF statement can span more than one line.one line.

Each statement consists of a command Each statement consists of a command and its associated parameters, and its associated parameters, terminated by a semicolon.terminated by a semicolon.

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SVF isn’t case sensitive and comments are SVF isn’t case sensitive and comments are indicated by exclamation point (!) or a pair indicated by exclamation point (!) or a pair of slashes (//) . Either '//' or '!' will of slashes (//) . Either '//' or '!' will comment out the remainder of the line. comment out the remainder of the line.

SVF is terminated with a carriage return.SVF is terminated with a carriage return.

Scan data within a statement is expressed as hexadecimal and is always enclosed in parentheses.

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SVFSVF commands can be grouped into three types:

state commands. offset commands. parallel commands.

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State Commands:

State commands are used to specify how the test sequences will traverse the IEEE Std 1149.1 TAP state machine.

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The following state commands The following state commands are supported:are supported:

ENDDR:Specifies default end state for DR scan operations.

ENDIR:Specifies default end state for IR scan operations.

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SDR = Scan Data Register : Performs an IEEE 1149.1 Data Register

scan.

SIR = Scan Instruction Register : Performs an IEEE 1149.1 Instruction

Register scan.

STATE: Forces the IEEE 1149.1 bus to a

specified stable state.

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RUNTEST: Forces the IEEE 1149.1 bus to a run state for a specified number of clocks

or a specified time period.

TRST = Test ReSeT : Controls the optional Test Reset line.

i.e. It activates or deactivates the optional test-reset signal of the IEEE Std 1149.1 bus.

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Parallel Commands:

Parallel commands allow SVF to combine serial and parallel sequences.

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The following parallel The following parallel commands are supported:commands are supported:

PIO = Parallel Input/Output : Specifies a parallel test pattern.

PIOMAP = Parallel Input/Output Map : Maps PIO column positions to a logical pin.

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Offset Commands:

Offset commands allow a series of SVF commands to be targeted toward a contiguous series of points in the scan path.

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The following offset commands are The following offset commands are supported: supported:

HDR = Header Data Register : Specifies a header pattern that is prepended to the beginning of subsequent DR scan

operations.

HIR = Header Instruction Register : Specifies a header pattern that is prepended to the beginning of subsequent IR scan operations.

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TDR = Trailer Data Register : Specifies a trailer pattern that is

appended to the end of subsequent DR scan operations.

TIR = Trailer Instruction Register: Specifies a trailer pattern that is

appended to the end of subsequent IR scan operations.

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Note #1:Note #1: These patterns need only be specified once and are included on each scan unless changed by a subsequent HDR, HIR, TDR, or TIR command.

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Note #2:Note #2: A scan operation is defined as the A scan operation is defined as the execution of an SIR or SDR command execution of an SIR or SDR command and any associated header or trailer and any associated header or trailer commands. commands.

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The following table lists each SVF state name used for each IEEE 1149.1 TAP state name:

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Note #3:Note #3: When transitioning from one state to When transitioning from one state to another, there is no need to specify each another, there is no need to specify each state.state.For exampleFor example, if the current state is RESET , if the current state is RESET and DRPAUSE was selected as the end state, and DRPAUSE was selected as the end state, the TAP moves from RESET through IDLE, the TAP moves from RESET through IDLE, DRSELECT, DRCAPTURE, DREXIT1 to DRSELECT, DRCAPTURE, DREXIT1 to DRPAUSE. DRPAUSE. i.e. have to just specify the current and end i.e. have to just specify the current and end states and not each intermediate step.states and not each intermediate step.

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Note #4:Note #4:

The simplicity of SVF is also one of itsThe simplicity of SVF is also one of its

major weaknesses.major weaknesses.

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An example of SVF file:An example of SVF file:

!Begin Test Program

TRST OFF; !Disable Test Reset lineENDIR IDLE; !End IR scans in IDLEENDDR IDLE; !End DR scans in IDLEHIR 8 TDI (00); !8-bit IR headerHDR 16 TDI (FFFF) TDO (FFFF) MASK (FFFF);!16-bit DR headerTIR 16 TDI (0000); !16-bit IR trailerTDR 8 TDI (12); !16-bit DR trailerSIR 8 TDI (41); !8-bit IR scanSDR 32 TDI (ABCD1234) TDO (11112222); !32-bit DR scanSTATE DRPAUSE; !Go to stable state DRPAUSERUNTEST 100 TCK ENDSTATE IRPAUSE; !RUNBIST for 100 TCKs!End Test Program

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References:References:

http://www.asset-intertech.com/support/http://www.asset-intertech.com/support/svf.html#accesssvf.html#access

http://focus.ti.com/lit/an/ssya002c/ssya002c.pdfhttp://focus.ti.com/lit/an/ssya002c/ssya002c.pdf

http://www.asset-intertech.com/support/svf.pdfhttp://www.asset-intertech.com/support/svf.pdf

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