DFPort

DFPorts are used to declare the points of ingress into and egress out of a DFBlock for different types of signals. The declaration of a DFPort instantiates a DFInterconnect, the reference of which is attached to the root node of the DFProject.

Ports can be connected to each other within a hierarchy level (i.e. parent-to-child, child-to-parent, or child-to-child) where the child is within the immediate children of the parent. A DFConnection is used to describe the link between two DFPorts, or between a DFConstantTie and a DFPort - the connection is attached to the DFBlock within its connections array.

As with every tag, DFPort inherits from DFBase, so has support for all of the core attributes (id, description, and attributes).

{
    "id": "my_block[my_port]",
    "description": "Human readable description of the port",
    "attributes": { },
    "name": "my_port",
    "type": "axi4",
    "count": 1,
    "direction": "IN",
    "block": "my_root.my_block"
}
Property Usage
name Name of the port, this automatically generates an ID of the form <BLOCK>[<PORT>].
type Type of the port, must refer to a DFInterconnect.
count How many signals should this port carry - each can be connected individually.
direction Is the port nominally IN, OUT, or INOUT. The DFInterconnect's role may reverse the data direction for some components.
block Hierarchical path to the parent block.

Note

On the DFBlock page there is some discussion about the idea of “principal” ports, which allows ports like clock and reset to be nominated so that they can be easily identified by later stages of processing.

Python API

class designformat.port.DFPort(name='', type=None, count=0, direction=None, block=None, description=None)

DesignFormat representation of a port (input, output or inout)

__init__(name='', type=None, count=0, direction=None, block=None, description=None)

Constructor for a port object.

Parameters

  • name – Name of the port

  • type – Interface type, which refers to a DFInterconnect

  • count – Number of signals carried by the port

  • direction – Whether an input or output

  • block – Reference to the parent DFBlock

  • description – Human-readable description of the port

addConnection(conn)

Add a new connection to this port, either to another port or a DFConstantTie

Parameters

conn – The connection

chaseConnection(index=0, path=None)

Chase a connection from the port to it’s ultimate destination, note that this function returns a tuple containing the port and the signal index.

Parameters

  • index – The signal index within the port to chase from

  • path – The current path chased up to this point (used by recursive calls)

check()

Sanity check that the direction is allowed

dumpObject(project)

Dump out this node so that it can be reloaded

Parameters

project – Project definition used to calculate references

findConnectionPath(remote_port, local_index=0, remote_index=0, path=None)

Try to find a connection pathway between this port and a remote port, this procedure can use both basic connectivity information and the address map to try and find interconnections. A flood search is used, with the shortest path being preferred.

Parameters

  • remote_port – The remote port we are trying to reach

  • local_index – The index of the signal within this port

  • remote_index – The index of the signal within the remote port

  • path – Used to track the path construction during recursion

getDriverPorts()

Return a list of ports that are driving this port

getInboundConnections()

Return just the inbound connections (where we are being driven)

getInterconnectType()

Returns the DFInterconnect that this connection represents

getOutboundConnections()

Return just the outbound connections (where we are the driver)

getReceiverPorts()

Return a list of ports that are driven by this port

getRelativeAddress(remote_port, local_index=0, remote_index=0)

Calculate the relative address to access a remote port via basic connectivity and any address maps. This leverages the findConnectionPath function to first identify a viable path, then works through the path to identify the base address of the port.

Parameters

  • remote_port – The port to resolve

  • local_index – Outbound signal index to start from

  • remote_index – Inbound signal index of the target

hierarchicalPath()

Returns a complete hierarchical path from the DFProject’s root node all the way down to this port.

loadObject(obj, root)

Reload this node from passed in object.

Parameters

  • obj – Description of this node

  • root – Root object in the tree

resolveAddress(address, index=0)

If this port is an initiator in an address map, resolve an address as if part of a transaction initiated through this port.

Parameters

  • address – The address to resolve

  • index – The index of the signal within the port initiating the transaction (default: 0)

Javascript API

class DFPort(name, type, count, direction, block, description)

DesignFormat representation of a port (input, output or inout)

Constructor for a port object.

Arguments

  • name (string) – Name of the port

  • type (string) – Interface type, which refers to a DFInterconnect

  • count (integer) – Number of signals carried by the port

  • direction (string) – Whether an input or output

  • block (DFBlock) – Reference to the parent DFBlock

  • description (string) – Human-readable description of the port

DFPort.addConnection(conn)

Add a new connection to this port, either to another port or a DFConstantTie

Arguments
DFPort.chaseConnection(index, path)

Chase a connection from the port to it’s ultimate destination, note that this function returns a tuple containing the port and the signal index.

Arguments

  • index (integer) – The signal index within the port to chase from

  • path (list) – The current path chased up to this point (used by recursive calls)

DFPort.check()

Sanity check that the direction is allowed

DFPort.dumpObject(project)

Dump out this node so that it can be reloaded

Arguments

  • project (DFProject) – Project definition used to calculate references

DFPort.findConnectionPath(remote_port, local_index, remote_index, path)

Try to find a connection pathway between this port and a remote port, this procedure can use both basic connectivity information and the address map to try and find interconnections. A flood search is used, with the shortest path being preferred.

Arguments

  • remote_port (DFPort) – The remote port we are trying to reach

  • local_index (integer) – The index of the signal within this port

  • remote_index (integer) – The index of the signal within the remote port

  • path (list) – Used to track the path construction during recursion

DFPort.getDriverPorts()

Return a list of ports that are driving this port

DFPort.getInboundConnections()

Return just the inbound connections (where we are being driven)

DFPort.getInterconnectType()

Returns the DFInterconnect that this connection represents

DFPort.getOutboundConnections()

Return just the outbound connections (where we are the driver)

DFPort.getReceiverPorts()

Return a list of ports that are driven by this port

DFPort.getRelativeAddress(remote_port, local_index, remote_index)

Calculate the relative address to access a remote port via basic connectivity and any address maps. This leverages the findConnectionPath function to first identify a viable path, then works through the path to identify the base address of the port.

Arguments

  • remote_port (DFPort) – The port to resolve

  • local_index (integer) – Outbound signal index to start from

  • remote_index (integer) – Inbound signal index of the target

DFPort.hierarchicalPath()

Returns a complete hierarchical path from the DFProject’s root node all the way down to this port.

DFPort.loadObject(obj, root, types)

Reload this node from passed in object.

Arguments

  • obj (object) – Description of this node

  • root (DFBase) – Root object in the tree

  • types (object) – Map from class name to class definition

DFPort.resolveAddress(address, index)

If this port is an initiator in an address map, resolve an address as if part of a transaction initiated through this port.

Arguments

  • address (integer) – The address to resolve

  • index (integer) – The index of the signal within the port initiating the transaction (default: 0)