Outline

Receive from data queue (polling).

C format

 ER      prcv_dtq (ID dtqid, VP_INT *p_data);

 ER      iprcv_dtq (ID dtqid, VP_INT *p_data);

Parameter(s)

I/O	Parameter	Description
I	ID dtqid;	ID number of the data queue.
O	VP_INT *p_data;	Data element received from the data queue.

Explanation

These service calls process as follows according to the situation of the data queue specified by the parameter dtqid.

- There is a data in the data queue.
This service call takes out the oldest data from the data queue and stores the data to the area specified by p_data.
When there is a task in the transmission wait queue, this service call stores the data sent by the task in the top of the transmission wait queue and moves it from the WAITING state (data transmission wait state) to the READY state.

- There is no data in the data queue and there is a task in the transmission wait queue.
These service calls store the data specified by the task in the top of the transmission wait queue to the area specified by p_data. As a result, the task is unlinked from the transmission wait queue and moves from the WAITING state (data transmission wait state) to the READY state, or from the WAITING-SUSPENDED state to the SUSPENDED state.
Note, this situation is caused only when the capacity of the data queue is 0.

- There is no data in the data queue and there is no task in the transmission wait queue.
These service calls return "E_TMOUT".

Return value

Macro	Value	Description
E_OK	0	Normal completion.
E_PAR	-17	Parameter error. - p_data == NULL
E_ID	-18	Invalid ID number. - dtqid < 0 - dtqid > VTMAX_DTQ
E_CTX	-25	Context error. - This service call was issued in the CPU locked state. - The iprcv_dtq was issued from task. - The prcv_dtq was issued from non-task. - This service call was issued in the status "PSW.IPL > kernel interrupt mask level".
E_MACV	-26	Memory access violation. (only for prcv_dtq) - Stack pointer points out of user stack for invoking task. - The operand-write access to the area indicated by p_data has not been permitted to the invoking task.
E_NOEXS	-42	Non-existent object. - The data queue specified by dtqid does not exist.
E_TMOUT	-50	Polling failure.