Switch

Hardware_Modeling/Bus_Switch_Ctrl
Block Name: Switch

Code File Location: VisualSim/actor/lib/bus/Switch

Block Overview

o    The Switch provides the functionality of both the blocking and non-blocking configuration, based on the parameter setting- Blocking_Mode.  

• The Non-blocking switch is a mesh crossbar switch with a point-to-point connection between each source (A_Source) and destination (A_Destination).  
• The blocking switch is a crossbar with a single bus resource, meaning that all the requests and data must flow through this single internal resource.
• The standard block has 4 Input and Output Device connections.  Additional ports can be added.  The only restriction is that the names must be in order.  So, the next input will be port9 and the next output will be port10, and so on.  This block does not supports Power estimation. 
• The ports are set in pairs- port/port2, port3/port4 and so on.  Any device or bus must be connected to this combination only.  You cannot connect DRAM to port5 and port8.  You must connect it to port5 and port6 as a combination.
• To additional devices beyond 4, the usre must add additional ports.  You cannot concatenate multiple switchs to create a bigger switch.

Description

Non-Blocking: This switch transfers requests from each Source (A_Source) to each Destination (A_Destination) in a First Come-First Serve order. Each Source-Destination combination has a separate queue. There are multiple channels assigned for each Point-to-Point connection.  

Blocking: This switch transfers requests from a Source (A_Source) to a Destination (A_Destination) in a First Come-First Serve order. There is a single internal queue and all transactions across the switch are placed in this queue.

Delay:

• For Read or any non-Write Transfer: (Overhead_Cycles + Address_Bits/Width_Bytes)*(1.0e-6/Speed_Mhz), where Overhead_Cycles corressponds to any hardware added delay or protocol conversion time, and the second part is the number of cycles for the address transfer.
• For Write: (Overhead + (A_Bytes_Sent /Width_Bytes))*(1.0e-6/Speed_Mhz), where Overhead_Cycles corressponds to any hardware added delay or protocol conversion time, and the second part is the number of cycles for the data transfer.
• If zero delay is required across the switch, the Speed_Mhz must be set to 0.0 and Overhead_Cycles = 0.

Note: The actual delay across the Switch could be greater than this value because of the queuing on the input side before transmitting based on the availability of the interface.

Commands: A_Command field contains the Command name. This can be Write or any other Type. The any other type will be considered a Read. 

Hello Messages: This block bypasses the "Hello Messages" from Architecture components to update the Routing Table for interfaces across multiple buses. No routing Table definitions are required for the devices connected to Buses that are directly connected to ports of this Switch. Do not connect a architecture device such as a Processor or DRAM directly to the Switch Port. Always use a Linear Port to connect the device. 

Required Fields: A_Command, A_Bytes_Sent, A_Source and A_Destination.

Demo Model

Refer the Non-blocking Switch and Blocking Switch demo models for more details.

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