|stemRef||-||A pointer to the opaque library reference whose heartbeat callback function pointer is to be set.|
|cbProc||-||The heartbeat callback function.|
|cbRef||-||Opaque reference to the user's data.|
|pErr||-||A pointer to an aErr variable that recieves the error code on exit from this routine.|
When the aStem library receives a heartbeat its default response is to send another heartbeat to maintain the link. A heartbeat callback function can do custom processing when the aStem library responds to a heartbeat. An example of a task that may be performed in response to a heartbeat is to flash a status light in an application. The cbRef pointer can refer to the user's application data.