What's New in Common Power Format, Version 2.0

2

---

What's Changed from CPF 1.0 to CPF 1.1

• New Features

  • Introduced Concept of Secondary Power Domain

  • Improved Hiearchical Flow

  • Isolation Enhancements

  • Level Shifter Enhancements

  • State Retention Enhancements

  • Power Switch Enhancements

  • Power Mode Enhancements

  • Improved Support for DVFS Designs

  • Other Improvements

• Command Change Summary

  • Obsoleted Command Options

  • Renamed Command Options

  • New Commands

  • New Command Options

  • Syntax Changes

New Features

Introduced Concept of Base and Derived Power Domains

CPF 1.1 introduces the concepts of base and derived power domains.

• A power domain whose primary power supply provides power to another power domain through some power switch network is called a base domain.

• A power domain that derives its power from another power domain through some power switch network is called the derived domain.

To support this concept the -base_domains option to the create_power_domain command. This enables specification and simulation of domain dependencies.

Introduced Concept of Secondary Power Domain

CPF 1.0 only had the concept of a power domain which was defined as collection of instances that use the same power supply during normal operation and that can be switched on or off at the same time.

However, physical cells with multiple power pins were hard to model. Therefore the concept of secondary power domain was introduced.

A power domain X is a secondary power domain of a special low power instance if the primary power and ground nets of the domain X provide the power supply to the secondary power and (or) ground pins of the instance.

The secondary domain can be used to

• Enable the simulation of always-on cell

• Enable the simulation of deep sleep mode of retention cell

• Enable the physical implementation of always-on, retention logic and power switches

To support this concept the following changes were made:

• Added -secondary_domain option to the create_isolation_rule and the create_state_retention_rule commands.

• Added identify_secondary_domain command.

Improved Hiearchical Flow

To improve the hierarchical flow, the following concepts were introduced:

• Introduced Concept of Domain Mapping

• Introduced Concept of Power Mode Control Group

• Introduced Concept of Macro Model

Other improvements include

• Improved IP Support

• Defined Precedence for Rules

• Enhanced CPF Readability

Introduced Concept of Domain Mapping

CPF1.0 did not support mapping a block-level power domain into a higher-level power domain.

For example, when creating a hierarchical design, the domains of an IP are created without knowledge of final use. By introducing the concept of domain mapping, mapped power domains are treated as a single power domain.

Domain mapping can be used to

• Merge a block-level power domain into a top-level power domain in a hierarchical flow

• Reconfigure block level power domains at the top level

Mapping power domains causes some complications such as

• How to handle rules defined for the block-level and top-level power domains.

• How to merge power modes

To support this concept the following changes were made:

• Added -domain_mapping option to the set_instance command.

• Added -honor_boundary_port_domain option to the set_design command.

For more information on domain mapping, refer to Power Domain Mapping Concepts.

Introduced Concept of Power Mode Control Group

CPF 1.0 only supported top-level power mode definitions. However, in a hierarchical flow, a block can have its own power mode definitions. To describe how the power modes at the top-level are related to the power modes of a block, the concept of power mode control group was introduced.

A power mode control group is a set of power domains with an associated set of power modes and mode transitions that apply to this group only. A power mode group can contain other power mode groups.

To support power mode control groups, the following changes were added:

• Added the set_power_mode_control_group command.

• Added the end_power_mode_control_group command.

• Added the -group_modes option to the create_power_mode command.

• Added the -group_views option in the create_analysis_view command.

For more information, refer to Power Mode Control Groups.

Introduced Concept of Macro Model

Proper modeling of macro cells (such as a RAM) with complex power network is important because it serves as a specification for the

• Implementation tool to properly hook up the power and ground pins of the IP at the top level

• Verification tool to check for consistency between the implementation and the constraints specified in the CPF.

• Simulation tool to verify the behavior

Because the macro cell has only a behavioral model to describe its functionality, implementation and verification tools have to rely on the CPF modeling of the internal power network using the boundary ports.

To support modeling of macro cells, the concept of macro model was introduced.

To support this concept the following changes were made:

• Added set_macro_model command

• Added end_macro_model command

• Added set_floating_ports command

• Added set_input_voltage_tolerance command

• Added set_wire_feedthrough_ports command

For more information, refer to Modeling a Macro Cell.

Improved IP Support

To improve support of IP's, the following changes were made:

• Added support for parameterized IP by adding the -paramater_mapping option to the set_design command.

• Added support for specifying isolation constraints at the inputs of an IP by making the -isolation_condition option in the create_isolation_rule command optional.

• The define_related_power_pins command was added to specify the relationship between the power and data pins for IPs that have more than one set of power / ground pins.

Defined Precedence for Rules

In a hierarchical flow, block-level and top-level domains each can have rules defined with them. When you map power domains, the associated rules must be handled properly.

To handle the rule precedence, two categories of CPF rules are considered:

• Specific rules explicitly specify the targeted design objects.

• Generic rules do not explicitly specify the targeted design objects, but the targeted design objects can be derived from some option specified with the rule.

The following general rules of precedence apply:

1. Specific rules have a higher priority than generic rules.

2. Generic rules specified with both the -from and -to options have a higher priority than those generic rules specified with only -from or -to option.

3. If multiple CPF rules with the same priority are applied to the same design objects, the last rule wins.

In addition, for a hierarchical flow, the following rules of precedence apply:

The following policies should be followed by all tools when a block-level CPF is integrated into the top-level CPF using the set_instance command:

1. Block-level rules always overwrite the top-level rules if both rules apply to the same objects at the block-level after domain mapping.

2. Top-level rules are only applied to block-level objects if the block-level objects have no rule specified and the block is not a macro model.

   In this case, the tools should issue a warning to inform users that top-level CPF rules are applied to the block.

3. Block-level rules are never propagated to the top level.

4. For more information on the precedence of rules, refer to the Rules chapter in the Common Power Format Language Reference.

Enhanced CPF Readability

To improve the readability of the CPF files, the following enhancements were made:

• The end_design statement can now contain the name of the module used with the corresponding set_design command.

• The end_macro_model statement can now contain the name of the macro cell used with the corresponding set_macro_model command.

Isolation Enhancements

The following enhancements were made:

• Added support for isolation cell without enable pin by adding -no_enable option to the define_isolation_cell command and the -no_condition option to the create_isolation_rule command.

  IP blocks can have special requirements for input ports. For example, when the signals driving these input ports are switched off, the signals must be held at specific values. For these signals, no isolation condition can be specified because the IP developer has no knowledge of how the IP will be used.

• Added support for a default isolation rule for a power domain by adding the -default_isolation_condition option to the create_power_domain command.

• Added support for tristate isolation output by adding the tristate value to the -isolation_output option of the create_isolation_rule command.

• Added support for instantiating the isolation logic in any logic hierarchy within a power domain by adding the -within_hierarchy option to the update_isolation_rules command.

• Added support for isolation cells that must be put in the on or off domain by adding the on and off values for the -valid_location option to the define_isolation_cell command.

Level Shifter Enhancements

The following enhancements were made:

• Added support for instantiating the level shifters in any logic hierarchy within a power domain by adding the -within_hierarchy option to the update_level_shifter_rules command.

• Improved support for level-shifter cells with an enable pin by adding the -enable option to the define_level_shifter_cell command.

• Added support for ground level shifter by adding the -ground_input_voltage_range, -ground_output_voltage_range, -input_ground_pin and -output_ground_pin options to the define_level_shifter_cell command.

• Added support for level shifter cells that can be put in the driving or receiving domain by adding the either value for the -valid_location option to the define_level_shifter_cell command.

State Retention Enhancements

The following enhancements were made:

• Added support for latches by adding the -target_type to the create_state_retention_rule command.

• Added support for level-sensitive save and restore control by adding the -restore_level and -save_level options to the create_state_retention_rule command.

• Added support to more accurately match the implied RTL behavior with gate-level models by adding the -restore_precondition, -save_precondition, and -secondary_domain options to the create_state_retention_rule command.

• Added support to specify a list of instances that must be excluded from replacement with state retention elements by adding the -exclude option to the create_state_retention_rule command.

• Added support for master-slave type state retention cells which have neither a save nor restore pin. For more information, refer to Handling Master-Slave Type Retention Cells.

Power Switch Enhancements

The following enhancements were made:

• Added capability to specify the resistance of the power switch per stage.

  To support this feature, the -on_resistance option of the define_power_switch_cell command was replaced with the -stage_x_on_resistance options, where x corresponds to the stage.

• Added capability to specify an acknowledge receiver condition for each stage of the power switch cells.

  To support this feature, the -acknowledge_receiver option of the update_power_switch_rule command was replaced with the -acknowledge_receiver_x options, where x corresponds to the stage.

Power Mode Enhancements

CPF 1.0 only covered either the on or off state of a power domain. However, there is a need to also be able to specify when a power domain is in standby mode and to support forward bias and reverse bias.

To support specification of the state of a power domain, the -state option with values on, off, and standby option was added to the create_nominal_condition command.

To improve the functional modeling of the biased state, the -ground_voltage option was added to the create_nominal_condition command.

To improve the implementation of designs using body bias, the -nmos_bias_voltage and -pmos_bias_voltage options were added to the create_operating_corner command.

To describe forward body biasing, you must specify -pmos_bias_voltage with a value smaller than the value of -voltage and -nmos_bias_voltage with a value greater than the value of -ground_voltage. Forward biasing can be used to improve performance in the on state.

To describe reverse body biasing, you must specify -pmos_bias_voltage with a value larger than the value of -voltage and -nmos_bias_voltage with a value smaller than the value of -ground_voltage. Reverse body biasing can be used to achieve the standby state.

To describe reverse source biasing, you must specify the voltage values for the power supply (-voltage) and ground supply (-ground_voltage) that cause the logic to be in the on or standby state.

Improved Support for DVFS Designs

• Added Capability to Specify Control Conditions for Different States of a Domain

• Added Support for Domain Specific Transition Time

Added Capability to Specify Control Conditions for Different States of a Domain

To define active state and conditions for each power domain, the -active_state_conditions option was added to the create_power_domain command.

Added Support for Domain Specific Transition Time

In CPF 1.0 mode transition times applied to all power domains involved in the same mode transition. The transition time could be specified in

• absolute time--using the -latency option of the create_mode_transition command

• clock cycles--using the using the -cycles option of the create_mode_transition command

In the CPF 1.0 extended version you can now specify a minimum and maximum number for the -latency and the -cycles option of the create_mode_transition command.

Starting with the CPF 1.0 extended version mode transition times can be specified per power domain. To specify the required time for a domain for a specific state transition, the following options were added to the update_power_domain command:

• -transition_latency {from_nom latency_list}

  Specifies the nominal condition of the starting power state, followed by a list of transition times to complete a transition to the next power state.

• -transition_cycles {from_nom cycle_list clock_pin}

  Specifies the nominal condition of the starting power state, followed by a list of transition cycles to complete the transition to the next power state, followed by the clock pin.

• -transition_slope

  Specifies the transition rate(s) for the supply voltage of the domain during any state transition of the domain.

The specified time can be used by simulation to simulate the domain transition time or used by physical implementation tool as constraint when designing the power distribution network

Other Improvements

• Added Capability to Identify Illegal Power Modes

• Added Capability to Associate User Attributes with An Analysis View

• Added Control over Assertion Evaluation

• Added Support for Equivalent Control Pins

• Equivalent Power and Ground Nets

• Refined Specification of SDC Files

• Change in Hierarchy Delimiter

• Change in Object Names

Added Capability to Identify Illegal Power Modes

To assert that a particular configuration of domain conditions and power mode control group conditions is illegal, the assert_illegal_domain_configurations command was added.

Added Capability to Associate User Attributes with An Analysis View

To support this feature, the -user_attributes option was added to the create_analysis_view command.

Added Control over Assertion Evaluation

By default, assertions remain active when the power domain is powered down. This may create a lot of false assertions.

To inhibit evaluation of any selected assertion instance when its related power domain is powered down the create_assertion_control command was added.

Added Support for Equivalent Control Pins

To define a list of this pins that are equivalent with a master control pin, the set_equivalent_control_pins command was added. The master control pin is part of the definition of a shutoff condition, isolation condition or state retention condition.

Equivalent Power and Ground Nets

If a power domain is implemented in multiple disjoint physical regions, each region has its own power and ground nets. To declare these power and ground nets equivalent to the primary power and ground nets of a power domain, the -equivalent_power_nets and -equivalent_ground_nets options were added to the update_power_domain command.

Refined Specification of SDC Files

Added capability to group SDC files with only hold or setup constraints by adding the -hold_sdc_files and -setup_sdc_files options to the update_power_mode command.

Change in Hierarchy Delimiter

Added the colon (:) as allowed hierarchy delimiter character, and removed the caret (^) as allowed hierarchy delimiter character.

Change in Object Names

Object names can no longer contain the dollar sign ($).

Command Change Summary

Obsoleted Command Options

Command	Obsolete Option(s)	Equivalent?
set_instance	-merge_default_domains	-domain_mapping The old option only allowed for merging of the default domains. The new option is more general.
update_isolation_rules	-combine_level_shifting	None By default, implementation tools should try to find a suitable cell that has both isolation and level-shifting functionality. See How to Handle Multiple Rules that Apply to a Physical Net.
	-library_set	None Implementation tools should automatically select valid cells from the library sets associated with the power domain through the update_nominal_condition or create_operating_corner commands.
update_level_shifter_rules	-library_set	None Implementation tools should automatically select valid cells from the library sets associated with the power domain through the update_nominal_condition or create_operating_corner commands.
update_power_domain	-max_power_up_time -min_power_up_time	-transition_latency -transition_cycles Because a power domain can be in a different on state (with different voltages) and it can also be in a standby state, a more fine grain specification of domain transition time was needed.
	-rail_mapping -library_set	None The options were initially added to check for power/ground connectivity for special cells with multiple power and ground pins. With the introduction of secondary power domain and domain mapping, this is no longer needed. All the power/ground net connections are described in CPF.
update_power_switch_rule	-library_set	None Implementation tools should automatically select valid cells from the library sets associated with the power domain through the update_nominal_condition or create_operating_corner commands.
update_state_retention_rules	-library_set	None Implementation tools should automatically select valid cells from the library sets associated with the power domain through the update_nominal_condition or create_operating_corner commands.

Renamed Command Options

Command	Old Option (1.0)	New Option (1.1)
create_mode_transition	-from_mode	-from
	-to_mode	-to
define_isolation_cell	-always_on_pin	-always_on_pins
define_level_shifter_cell	-always_on_pin	-always_on_pins
	-output_voltage_input_pin	-enable
define_power_switch_cell	-on_resistance	-stage_x_on_resistance
define_state_retention_cell	-always_on_pin	-always_on_pins
update_power_domain	-internal_power_net	-primary_power_net
	-internal_ground_net	-primary_ground_net
update_power_switch_rule	-acknowledge_receiver	-acknowledge_receiver_x
update_state_retention_rules	-cell	-cells

Note:  For backward-compatibility, the old names are also supported.

Changed Command Option Value

Command	Option	Old Value	New Value
create_ground_nets	-voltage	string	{float|voltage_range}
create_isolation_rule	-isolation_output	{high|low| hold}	{high|low|hold|tristate}
create_mode_transition	-cycles	integer	[integer:]integer
	-latency	float	[float:]float
create_power_nets	-voltage	string	{float|voltage_range}
define_isolation_cell	-valid_location	{from|to}	{from|to|on|off}
define_level_shifter_cell	-valid_location	{to|from}	{to|from|either}
define_library_set	-libraries	library file list	list of library files and library groups
update_power_switch_rule	-acknowledge_receiver_x	pin	expression

New Commands

assert_illegal_domain_configurations

create_assertion_control

define_related_power_pins

end_macro_model

end_power_mode_control_group

get_parameter

identify_secondary_domain

include

set_equivalent_control_pins

set_floating_ports

set_input_voltage_tolerance

set_macro_model 

set_power_mode_control_group

set_wire_feedthrough_ports

New Command Options

Command	New Option/Argument
create_analysis_view	-group_views
	-user_attributes
create_ground_nets	-external_shutoff_condition
create_isolation_rule	-no_condition
	-secondary_domain
create_nominal_condition	-ground_voltage
	-state
create_operating_corner	-ground_voltage
	-nmos_bias_voltage
	-pmos_bias_voltage
create_power_domain	-active_state_conditions
	-base_domains
	-default_isolation_condition
	-default_restore_level
	-default_save_level
	-external_controlled_shutoff
create_power_mode	-group_modes
create_state_retention_rule	-exclude
	-restore_level
	-restore_precondition
	-save_level
	-save_precondition
	-secondary_domain
	-target_type
define_isolation_cell	-no_enable
define_level_shifter_cell	-enable
	-ground_input_voltage_range
	-ground_output_voltage_range
	-input_ground_pin
	-output_ground_pin
	-power
define_power_switch_cell	-enable_pin_bias
	-gate_bias_pin
	-stage_x_on_resistance
define_state_retention_cell	-always_on_components
	-cell_type
end_design	module
end_macro_model	macro_cell
identify_power_logic	-module
set_design	-honor_boundary_port_domain
	-parameters
set_instance	-design
	-domain_mapping
	-model
	-parameter_mapping
update_isolation_rules	-within_hierarchy
update_level_shifter_rules	-within_hierarchy
update_power_domain	-equivalent_power_nets
	-equivalent_ground_nets
	-transition_cycles
	-transition_latency
	-transition_slope
update_power_mode	-hold_sdc_files
	-setup_sdc_files
update_power_switch_rule	-gate_bias_net
update_state_retention_rules	-set_reset_control

Syntax Changes

Command	New Option
create_isolation_rule	-pins option must be specified with -from, -to or both options
	-isolation_condition option is now optional
create_level_shifter_rule	-pins option must be specified with -from, -to or both options
create_power_domain	options -instances, -boundary_ports and -default are no longer exclusive
	modified syntax for -default_save_xx and -default_restore_xx options
create_state_retention_rule	modified syntax for the -restore_edge and -save_edge options
define_always_on_cell	allow specification of combination of -power_switchable and -ground_switchable options
define_level_shifter_cell	made step in voltage range optional: lower_bound:upper_bound[:step]
define_state_retention_cell	allow specification of combination of -power_switchable and -ground_switchable options
	modified syntax for -save_function and -restore_function options

For support, see http://www.cadence.com/support or try Cadence's SourceLink service.

Copyright © 2013, Cadence Design Systems, Inc.
All rights reserved.
Legal notices and trademark attributions