E
Unsupported Elements of Verilog-AMS
The Cadence® Verilog®-AMS language is specified in the Verilog-AMS Language Reference Manual: Analog & Mixed-Signal Extensions to Verilog HDL, produced by Open Verilog International. The Cadence implementation of Verilog-AMS does not support all of the specified elements of the Verilog-AMS language in all the contexts in which the language specification says they are to be supported.
The tables in this section list the unsupported elements according to the following classifications:
-
Unsupported elements that should be supported in behavioral contexts, such as: expressions; initial, always, and analog blocks; and user-defined tasks and functions.
-
Unsupported elements that should be supported in analog contexts, such as analog blocks and analog functions.
-
Unsupported elements that should be supported in structural contexts such as those that exist outside behavioral contexts and have to do with hierarchy, natures, and disciplines.
-
Unsupported elements that should be supported in digital contexts, such as initial and always blocks, and user-defined digital tasks and digital functions.
Unsupported Elements for Behavioral Contexts
|
Feature
|
Comment
|
|
Net attributes, except for net.potential.abstol and net.flow.abstol, which are supported
|
|
|
String variables
|
Cannot be assigned in analog block. Cannot be used in $strobe in the analog block.
|
|
Using probes containing vector net elements in a digital block.
|
|
|
Out-of-module references
|
Not supported to analog nets, branches, or nature attributes.
|
|
Standard math and transcendental functions
|
Inside the analog block, expressions that contain hierarchical references are not supported. Domain ranges are checked only for exp, sqrt, pow, and atan2.
|
|
$rdist functions
|
Supported in analog contexts but not in digital contexts.
|
|
Global events
|
The @analog_identifier form is not supported.
|
|
@timer
|
Not supported in the digital context.
|
|
$realtime
|
Not supported in the analog context. Use $abstime instead, in the analog context.
|
Unsupported Elements for Behavioral Analog Contexts
|
Feature
|
Comment
|
|
Parameters used to specify ranges for the generate statement
|
|
|
Parameter declarations
|
Not supported in analog user-defined functions.
|
|
The genvar statement
|
|
|
Arrays passed to functions
|
|
|
ddt (time derivative) operator
|
Nesting is not allowed. For example, ddt(ddt()) is prohibited. The abstol argument has no effect. A nature cannot be used as an argument.
|
|
Laplace transform filters
|
Parameter-sized array arguments are not supported.
|
|
Analog functions
|
Parameters are not allowed as arguments.
|
|
Analog vector nets
|
Not supported for the Tcl value command.
|
|
Digital transition sensitivities
|
Transition sensitivities such as @dVal are not supported in analog contexts. Event sensitivities such as
@(posedge dVal or negedge dVal)
must be used instead.
|
|
The concatenation operator
|
|
|
$stime
|
|
|
$time
|
|
|
$monitor and $fmonitor
|
|
|
$monitor off/on
|
|
|
$printtimescale
|
|
|
$timeformat
|
|
|
$bitstoreal
|
|
|
$itor
|
|
|
$realtobits
|
|
|
$rtoi
|
|
|
$readmen used with the %b, %h, and %r specifications.
|
|
Unsupported Elements for Structural Contexts
|
Feature
|
Comment
|
|
Derived natures
|
|
|
Overriding nature attributes from disciplines
|
|
|
Array ranges for nets
|
|
|
Array ranges for ground nodes
|
|
|
Parameter arrays
|
Parameter array declarations are not supported. Parameter array assignments are supported only in analog primitives.
|
|
Module instantiation inside a generate block
|
Generate blocks, because they can be used only in analog blocks, can contain only behavioral code.
|
|
Parameter-sized vector nets
|
|
|
User-defined attributes
|
Only the Cadence huge, blowup, and maxdelta attributes are supported.
|
|
Vector branches
|
|
|
Vector arguments for simulator functions
|
|
|
Vector ground nodes
|
|
|
Parameter-sized ports
|
|
|
Out-of-module references
|
Supported for voltage probes on nets. Not supported for branches, or for nature attributes.
|
|
Discipline resolution
|
If out-of-module references are used in port connections, the port discipline is not used to determine the discipline of the out-of-module reference.
|
|
net_resolution
|
|
|
Nodesets on continuous nets
|
|
The next list contains only VPI functions. The unsupported aspect of these functions is that they cannot be called with wreal arguments, digital real vectors, or analog arguments of any kind.
Unsupported Elements for Behavioral Digital Contexts When wreal Arguments Are Used
|
Feature
|
Comment
|
|
@timer
|
|
|
$compare
|
|
|
$strobe_compare
|
|
|
$countdrivers
|
|
|
$deposit
|
|
|
$incpattern_read
|
|
|
$async$and$array
|
|
|
$async$nand$array
|
|
|
$async$or$array
|
|
|
$async$nor$array
|
|
|
$sync$and$array
|
|
|
$sync$nand$array
|
|
|
$sync$or$array
|
|
|
$sync$nor$array
|
|
|
$async$and$plane
|
|
|
$async$nand$plane
|
|
|
$async$or$plane
|
|
|
$async$nor$plane
|
|
|
$sync$and$plane
|
|
|
$sync$nand$plane
|
|
|
$sync$or$plane
|
|
|
$sync$nor$plane
|
|
|
$q_initialize
|
|
|
$q_full
|
|
|
$q_remove
|
|
|
$q_add
|
|
|
$q_exam
|
|
|
$scope
|
|
|
$dumpports
|
|
|
$dumpports_close
|
|
|
$lsi_dumpports
|
|
|
$lsi_close
|
|
|
$writememb
|
|
|
$writememh
|
|
|
$recordvars
|
|
|
$recordfile
|
|
|
$recordon
|
|
|
$recordoff
|
|
|
$signalscan
|
|
|
$signalscankill
|
|
|
$signalscanabort
|
|
|
$recordabort
|
|
|
$recordclose
|
|
|
$recordfilecopy
|
|
|
$recordfilechange
|
|
|
$signalscanconnect
|
|
|
$signalscancommand
|
|
|
$recordsetup
|
|
The Cadence™ Verilog®-AMS language is specified in Annex C of the Verilog-AMS Language Reference Manual: Analog & Mixed-Signal Extensions to Verilog HDL, produced by Open Verilog International. The Cadence implementation of Verilog-AMS does not support all of the specified elements of the Verilog-AMS language in all the contexts in which the language specification says they are to be supported.
The tables in this section list the unsupported elements according to the following classifications:
-
Unsupported elements that should be supported in behavioral contexts, such as expressions; initial, always, and analog blocks; user-defined tasks and functions.
-
Unsupported elements that should be supported in analog contexts, such as analog blocks and analog functions.
-
Unsupported elements that should be supported in structural contexts such as those outside behavioral contexts, and having to do with hierarchy, natures, and disciplines.
-
Unsupported elements that should be supported in digital contexts, such as initial and always blocks, and user-defined digital tasks and digital functions.
Unsupported Elements for Behavioral Contexts
|
Feature
|
Comment
|
|
Hierarchical names, except for node.potential.abstol and node.flow.abstol, which are supported
|
|
|
Using 1’b1 constant specification
|
|
|
String variables
|
Cannot be assigned in analog block. Cannot be used in $strobe in the analog block.
|
|
Using probes containing vector net elements in a digital block.
|
|
|
String variables
|
|
|
The %b and %B format characters
|
|
|
The \ddd octal specification of a character
|
|
|
The concatenation operator
|
|
|
Enforcement of input, output, and inout
|
|
|
Out-of-module references
|
Not supported to analog nets, branches, or nature attributes.
|
|
Case equality (=== and !==) operators
|
|
|
casex and casez statements
|
|
|
Standard math and transcendental functions
|
Outside the analog block, arguments to functions must be constant expressions. Inside the analog block, expressions that contain hierarchical references are not supported. Domain ranges are checked only for exp, sqrt, pow, and atan2.
|
|
$rdist functions
|
|
|
Global events
|
The @analog_identifier form is not supported.
|
|
@timer
|
Not supported in the digital context.
|
|
Driver access functions
|
Driver_update is not supported.
|
|
$realtime
|
Not supported in the analog context. In that context, use $abstime instead.
|
|
$stime
|
|
|
$time
|
|
|
$monitor and $fmonitor
|
|
|
The %b, %o, and %h specifications for $display, $fdisplay, $write, $fwrite, $monitor, $fmonitor, $strobe, and $fstrobe
|
|
|
$monitor off/on
|
|
|
$printtimescale
|
|
|
$timeformat
|
|
|
$bitstoreal
|
|
|
$itor
|
|
|
$realtobits
|
|
|
$rtoi
|
|
|
$readmen used with the %b, %h, and %r specifications.
|
|
|
$random
|
The seed must be an integer constant expression, not an unsigned integer.
|
Unsupported Elements for Behavioral Analog Contexts
|
Feature
|
Comment
|
|
Parameters used to specify ranges for the generate statement
|
|
|
Parameter declarations
|
Not supported in analog user-defined functions.
|
|
The genvar statement
|
|
|
Arrays passed to functions
|
|
|
Accessing X and Z bits of a discrete net from a continuous context.
|
|
|
ddt (time derivative) operator
|
Nesting is not allowed. For example, ddt(ddt()) is prohibited. The abstol argument has no effect. A nature cannot be used as an argument.
|
|
idt (time integral) operator
|
The abstol argument has no effect. A nature cannot be used as an argument.
|
|
idtmod (circular integrator) operator
|
The abstol argument has no effect. A nature cannot be used as an argument.
|
|
Transition filter
|
The time_tol argument is not supported.
|
|
Laplace transform filters
|
Parameter-sized array arguments are not supported.
|
|
Analog functions
|
Parameters are not allowed as arguments.
|
|
‘default_transition directive
|
|
|
analog vector nets
|
Not supported for the Tcl value command.
|
Unsupported Elements for Structural Contexts
|
Feature
|
Comment
|
|
Ordered parameter lists in hierarchical instantiation
|
Not supported for analog primitives.
|
|
Named nodes in hierarchical instantiation
|
|
|
Connecting the ports of instantiated analog primitives to digital wires
|
|
|
Derived natures
|
|
|
Overriding nature attributes from disciplines
|
|
|
Array ranges for nets
|
|
|
Array ranges for ground nodes
|
|
|
Parameter arrays
|
Parameter array declarations are not supported. Parameter array assignments are supported only in analog primitives.
|
|
Parameter-sized vector nets
|
|
|
The defparam statement
|
|
|
The ground declaration
|
|
|
User-defined attributes
|
Only the Cadence huge, blowup, and maxdelta attributes are supported.
|
|
Vector branches
|
|
|
Vector arguments for simulator functions
|
|
|
Vector ground nodes
|
|
|
Parameter-sized ports
|
|
|
Out-of-module references
|
Not supported to analog nets, branches, or nature attributes.
|
|
Discipline resolution
|
If out-of-module references are used in port connections, the port discipline is not used to determine the discipline of the out-of-module reference.
|
|
net_resolution
|
|
Many of the items in the next list are VPI functions. The unsupported aspect of these functions is that they cannot be called with wreal arguments, digital real vectors, or analog arguments of any kind.
Unsupported Elements for Behavioral Digital Contexts
|
Feature
|
Comment
|
|
Analog transition sensitivity
|
Not supported in digital contexts.
|
|
$compare
|
|
|
$strobe_compare
|
|
|
$countdrivers
|
|
|
$deposit
|
|
|
$incpattern_read
|
|
|
$async$and$array
|
|
|
$async$nand$array
|
|
|
$async$or$array
|
|
|
$async$nor$array
|
|
|
$sync$and$array
|
|
|
$sync$nand$array
|
|
|
$sync$or$array
|
|
|
$sync$nor$array
|
|
|
$async$and$plane
|
|
|
$async$nand$plane
|
|
|
$async$or$plane
|
|
|
$async$nor$plane
|
|
|
$sync$and$plane
|
|
|
$sync$nand$plane
|
|
|
$sync$or$plane
|
|
|
$sync$nor$plane
|
|
|
$q_initialize
|
|
|
$q_full
|
|
|
$q_remove
|
|
|
$q_add
|
|
|
$q_exam
|
|
|
$scope
|
|
|
$dumpports
|
|
|
$dumpports_close
|
|
|
$lsi_dumpports
|
|
|
$lsi_close
|
|
|
$writememb
|
|
|
$writememh
|
|
|
$recordvars
|
|
|
$recordfile
|
|
|
$recordon
|
|
|
$recordoff
|
|
|
$signalscan
|
|
|
$signalscankill
|
|
|
$signalscanabort
|
|
|
$recordabort
|
|
|
$recordclose
|
|
|
$recordfilecopy
|
|
|
$recordfilechange
|
|
|
$signalscanconnect
|
|
|
$signalscancommand
|
|
|
$recordsetup
|
|
The items in the next list are deprecated features. The Cadence implementation of Verilog-AMS supports these features, but might not in the future. These features are no longer supported in the standard specification of the language.
Deprecated features
|
Deprecated feature
|
To comply with the current standard,...
|
|
$dist_ functions in the analog block
|
Consider using the $rdist functions.
|
|
generate statement in the analog block
|
Use the genvar statement.
|
|
The second argument of the cross operator being a non-integer type
|
Change the second operator to an integer type.
|
|
Using for, while and repeat loop statements for the timer function
|
Use a genvar loop for the timer function.
|
|
Unassigned variables
|
Assign each variable. Unassigned variables are considered digital variables.
|
|
generate
|
Use a genvar loop instead.
|
|
The second argument of the last_crossing operator being a non-integer type
|
Change the second operator to an integer type.
|
The items in the next list are Cadence extensions. These features are not part of the standard specification of the language.
Cadence extensions
|
Feature
|
|
|
Cadence syntax for attributes
|
|
|
mfactor attribute
|
|
|
dynamicparams
|
|
|
$cds_iprobe
|
|
|
Inherited parameters
|
|
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