Subsystem Considerations

By default, the TestStand Batch process model executes a copy of the test program for each site simultaneously without changing any code by creating a test socket for each site. Each test socket runs in parallel and synchronizes at the beginning and end of the batch. However, each copy of the test program executes independently on each test socket and does not synchronize over each step within the test program execution shown in the following figure.

ECU Software Toolkit site numbers do not always directly correspond to test socket indexes.

Sharing Instrumentation Resources

Executing a copy of the test program for each socket works well when you use dedicated hardware for each DUT. In reality, however, it is more likely that multiple DUTs share the same instrumentation, which requires you to write test code to account for instrumentation sharing. In the following example, Test 1 and Test 3 share instrumentation resources.

Test 1 uses instrumentation shared between Sites 0 and 1 and between Sites 2 and 3. Test 3 uses instrumentation shared among all four sites. In this example, Sites 0 and 1 must synchronize at the first step, and Sites 2 and 3 must also synchronize at the first step. Because Sites 0 and 1 do not have to wait on Sites 2 and 3, each site group can continue testing after the first test is done. However, all sites must synchronize for Test 3 because of the dependency on instrumentation resources. After Test 3 completes, all sites can execute in parallel.

Using instrumentation multiplexed across sites or instruments that access multiple sites simultaneously introduce the following synchronization challenges:

• Multiplexed sharing—You can use a multiplexer to connect a single instrument to multiple pins on the same DUT or on multiple DUTs. In this case, each site or pin must wait until an instrument is free.
• Simultaneously sharing instruments—You can connect a single instrument that supports simultaneous access to its resources to multiple pins on the same DUT or multiple DUTs, but for optimal performance you must synchronize the operations to occur at the same time. In this case, one code module can take measurements for multiple sites and report the measurements back to each test socket.
• Relay sharing—Run any sites that share relays in the same subsystem.