The dashed lines in the following diagram show how messages from the DUMP and CHG_COLOR phases are coordinated by the Batch Executive. The request messages are sent from the phases to the Batch Executive (using their respective REQUEST parameters) at various places in the phase logic. The requests are a means of acquiring resources or coordinating activities between one or more phases (in this case, the DUMP and CHG_COLOR phases). For phase coordination there are two types of requests we will use: Send message to another phase (52nn) and Wait for a message (55nn).
Once a request is received, the Batch Executive attempts to carry out the request. For any Wait message request that is received, there must be a corresponding Send message request before the Batch Executive can respond. For example, if one phase sends a request message indicating that it is waiting to transfer material (Wait message), then the Batch Executive will look for another phase to send a request message indicating that it is ready to transfer material (Send message).
After the Batch Executive receives both requests, it clears the REQUEST parameters for both phases by setting them to a value of 0. This indicates to the phases that their respective requests have been successfully processed.
The other type of request message we will use in this example is the Acquire a single resource request. For this type of request, the Batch Executive checks to see if the resource being requested is available. If it is, it acquires the resource for the phase. If the resource is not available, the Batch Executive will wait until the resource becomes available and then acquire it. Once it acquires the resource it clears the phase's REQUEST parameter.
Later, when we manually run through this example, you will act as the Batch Executive and set the values to 0 to acknowledge the requests.
In this example, the Equipment ID for the COLOR_HEADER is 15. Your ID may be different. Substitute your ID wherever 15 is used in this example.
