3.6. Test Chip IP

Chipyard includes a Test Chip IP library which provides various hardware widgets that may be useful when designing SoCs. This includes a Serial Adapter, Block Device Controller, TileLink SERDES, and TileLink Switcher.

3.6.1. Serial Adapter

The serial adapter is used by tethered test chips to communicate with the host processor. An instance of RISC-V frontend server running on the host CPU can send commands to the serial adapter to read and write data from the memory system. The frontend server uses this functionality to load the test program into memory and to poll for completion of the program. More information on this can be found in Chipyard Boot Process.

3.6.2. Block Device Controller

The block device controller provides a generic interface for secondary storage. This device is primarily used in FireSim to interface with a block device software simulation model. The default Linux configuration in firesim-software

To add a block device to your design, add HasPeripheryBlockDevice to your lazy module and HasPeripheryBlockDeviceModuleImp to the implementation. Then add the WithBlockDevice config mixin to your configuration.

3.6.3. TileLink SERDES

The TileLink SERDES in the Test Chip IP library allow TileLink memory requests to be serialized so that they can be carried off chip through a serial link. The five TileLink channels are multiplexed over two SERDES channels, one in each direction.

There are three different variants provided by the library, TLSerdes exposes a manager interface to the chip, tunnels A, C, and E channels on its outbound link, and tunnels B and D channels on its inbound link. TLDesser exposes a client interface to the chip, tunnels A, C, and E on its inbound link, and tunnels B and D on its outbound link. Finally, TLSerdesser exposes both client and manager interface to the chip and can tunnel all channels in both directions.

For an example of how to use the SERDES classes, take a look at the SerdesTest unit test in the Test Chip IP unit test suite.

3.6.4. TileLink Switcher

The TileLink switcher is used when the chip has multiple possible memory interfaces and you would like to select which channels to map your memory requests to at boot time. It exposes a client node, multiple manager nodes, and a select signal. Depending on the setting of the select signal, requests from the client node will be directed to one of the manager nodes. The select signal must be set before any TileLink messages are sent and be kept stable throughout the remainder of operation. It is not safe to change the select signal once TileLink messages have begun sending.

For an example of how to use the switcher, take a look at the SwitcherTest unit test in the Test Chip IP unit tests.