Method and device for the counting and management of asynchronous events emitted by peripheral devices in a data processing system

DETAILED DESCRIPTION The present invention provides a solution to this problem by proposing a method of accounting and checking asynchronous messages utilizing the technological means of the input-output master control unit as well as the firmware microprograms which control this master control unit.
In this input-output master control unit, the firmware effects operations for filtering and conservation of messages which were up until then ensured by the logic; this results in a simplification of the logic, an increase in performance of the machine and the safeguarding of excess numbers of asynchronous messages which the logic was lead to abandon.
Briefly stated, and in accordance with the invention, a method for counting the number of messages emitted by the peripherals linked to a microprogrammed or analog data processing system is characterized in that, for each appearance of an asynchronous event on a peripheral device, this event is signalled to the firmware; the firmware thus solicited forms a message intended to inform the logic; then the firmware places this message in a primary waiting queue where this message waits until the moment when the logic can take this message into account; at the moment of taking it into the primary waiting queue, the firmware increases by one unit the contents of a transmitted event counter assigned to the peripheral device which has originated the asynchronous events; at the moment of taking into account by the logic, the latter requests the firmware to decrease this count.
According to another aspect of the method of the invention, before placing the message intended to inform the logic in the primary waiting queue, the firmware compares the contents of the counter assigned to the peripheral device with the contents of a boundary register containing a limit value.
If the contents of this counter do not exceed the limit value, the message is placed in the primary waiting queue; if the contents of this counter exceed the limit value, the firmware places the message in a secondary waiting queue, also called the limit value overflow waiting queue