The on-board serial ports support connector testing. The connector test requires the null modem and plug connectors described in Building Test Connectors.
There are a variety of connector loopback paths available. The internal loopback paths do not require an external connector. The availability of the loopback paths depends on the device. The zs(7D)device has an internal path for synchronous mode and the se(7D)device has an internal path for asynchronous mode. The exact type of loopback connector required depends on the system I/O panel.
The connector for the null modem A-to-B option is a female-to-female plug. The pin configuration is the same as the one described in see 9-Pin to 9-Pin Port-to-Port Cable.
The connector for the plug A-to-A option is described in 9-Pin Female Single-Port Plug.
The Sbus and PCI bus SunHSI boards also support connector testing.
For x86 systems, only external loopback is supported on serial ports. However, this applies only to systems that do not use their serial ports for system management. For those systems, loopback testing is not supported.