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This is a guest post by Qi Wang, Sr. Architect for the Cadence Low Power Solution, providing more information on what is contained in the recently-announced CPF version 1.1.
There are many major improvements in
the new Si2 CPF version 1.1, and I would like to provide more details on a few of them:
Hierarchical Flow Support
CPF 1.1 has all the syntax needed to
create a complex low power IP and integrate it into the top level design by using the powerful new concept of
power domain mapping.
Power domain mapping specifies how a IP level power domain should be
integrated into a chip level power domain. The same specification is used for RTL power-aware simulation,
power-aware logic synthesis, physical implementation, sign-off analysis and low power verification. It not
only enables seamlessly handoff low power IP's between design teams but also enables
closed-loop verification of low power designs in hierarchical flows.
There are two major enhancements in IP re-use
support. First is support for parameterized
low power IPs. This enables IP vendors to create a single low
power IP to be used by different users with different power configurations,
depending on their specific needs.
the introduction of CPF macro
models. CPF macro models are a unique way to model any low power customer IP,
such as dual-rail RAMs or flash memories, multi-rail analog blocks etc. It not only has the syntax to
describe the low power structure of the IP using only the boundary pins of the
IP, but also has the semantics to drive
the simulation of such IPs at the block level as well as chip level. Traditional low power IP validation only takes
place at the block level. With the CPF macro model specification, low power custom IPs can also be simulated and
verified at chip level along with the low power features at chip level by combining the macro model CPF with
the chip-level CPF files.
Secondary Power Domain
Many low power cells - such as
always-on buffers, retention cells, and isolation cells - have two power supplies. The new secondary power domain
concept enables modeling of such logic even at the RTL. Additionally, using the same
specification, implementation tools can automatically connect the correct supply nets to the secondary power
or ground pin of such low power cells without any user intervention.
This not only simplifies the flow and
eliminates the possibility of human error, more importantly it ensures that the implementation tools implement exactly what has been verified at RTL using the same CPF
Disjoint Power Domain
In real designs, an RTL or logical-level power domain may have to be implemented into different physical regions
with unconnected local power supplies.
Such implementation of a power domain is also called Disjoint Power Domain.
CPF 1.1 allows specification of such
implementation details later in the design cycle while maintaining the RTL power domain specification as
the golden reference. Implementation tools can use the disjoint power domain
specification to drive physical implementation
while verification tools using the same specification to check for the correctness of power connections
upon the physical netlist.
Equivalent Control Signals
In low power designs, there are many
control signals to control low power features such as power gating, state
retention and isolation. Typically, a single
control signal is used to turn on or enable a set of devices. However in very large designs, such control signals may fanout to
thousands of loads. To control the rush current due to the simultaneous turn-on
of all connected devices, designers
typically use time-staged control signals to turn on the devices group-by-group. Such control signals are called equivalent control signals
with respect to the master control signal. CPF 1.1 allows the specification of the master and equivalent control
signals at RTL to enable RTL simulation of such designs. The same specification
is used to drive implementation to optimize the
fanouts of each control signal, depending on the physical placement. Verification
tools use the same specification to check the
correctness of the implementation of the control logic.
Full Support for DVFS Design Verification and MMMC Implementation
CPF 1.1 is enhanced to model the power mode-specific domain transition time of any general dynamic voltage-frequency-scaling (DVFS) design. This specification can be used for RTL simulation of
the design with sophisticated real delay models to simulate the dynamic
behavior of a DVFS design.
The same specification can be later
on refined to setup multi-mode multi-corner (MMMC) analysis and optimization at the implementation stage.