ibrda() is similar to ibrd() except it operates asynchronously. ibrda() does not wait for the reception of the data bytes to complete, but rather returns immediately.
While an asynchronous operation is in progress, most library functions will fail with an EOIP error. In order to sucessfully complete an asynchronous operation, you must call ibwait() until the CMPL bit is set ibsta. Asynchronous operations may also be aborted with an ibstop() or ibonl() call.
The value of ibsta is returned.