JPH01140362A - Channel controller - Google Patents

Abstract

PURPOSE:To prevent the overrun of data from being generated by comparing the bi-count of a pre-fetch CCW with a prescribed value, and performing the pre-fetch operation of the next CCW with a low priority order when the bi-count is equal to or exceeds the prescribed value, and with a high priority order when it is less than the prescribed value. CONSTITUTION:A comparator 4 which compares the bi-count of a channel command word (CCW) read out from a main storage device 1 with the prescribed value is provided. And the bi-count of the pre-fetch CCW is compared with the prescribed value by the comparator 4, and the pre-fetch processing of the next CCW is performed with the low priority order level when the bi- count of the CCW is equal to or exceeds the prescribed value, and with the high priority order level when it is less than the prescribed value. In such a way, it is possible to evade the unrequired continuous operation of a device or interruption from another channel in the case of requiring a fast processing, and to reduce the generation of the overrun of the data.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a channel control device connected to a main storage device and controlling a plurality of channel devices.

[Prior Art] Conventionally, in this type of channel control device, a channel command word (hereinafter referred to as CCW) is used to prevent data transfer of an input/output interface from being interrupted during data chaining.

) is prefetched and stored, and when a data chain is requested from the channel device, the prefetched CCW is sent to the channel device as data transfer information, and the next CCW is prefetched in order to prepare for the next data chain. was doing.

[Problem that the invention seeks to solve]

In the conventional channel control device described above, if a processing request with a higher priority is interrupted from another channel device during CCW preemption processing, the processing is preemptively interrupted and the request for the higher priority processing is executed. Therefore, the period of prefetching processing that is currently being processed becomes longer, and the prefetching is not completed by the time of the next data chain request from the corresponding channel device, resulting in a data overrun.

[Means for Solving the Problems] The channel control device of the present invention has an area corresponding to each channel device, a prefetch area in which channel command words prefetched from the main memory are stored, and a comparator that compares the byte count of the channel command word read from the channel with a predetermined value; and a pre-emption priority flip-flop that stores the comparison results of the comparator and is composed of a plurality of flip-flops corresponding to each channel device. a prefetch control unit that prefetches a channel command word from a main memory and stores the channel command word in an area corresponding to the channel device in the prefetch area; and an interrupt for data transfer from each channel device. An interrupt control unit that accepts requests creates data transfer information using the channel command word read from the main memory, sends it to the channel device, determines the data chain flag of the channel command word, and instructs the data chain. If there is, instruct the preemption control unit to preempt the channel command word,
When a transfer instruction is received from the interrupt control unit in response to an interrupt request from each channel device, a preemption channel command word is extracted from the preemption area and data transfer information is sent to the channel device. If the data chain flag of indicates a data chain, the flip-flop corresponding to the channel device in the pre-emption priority flip-flop group is set so that the byte count of the channel command word is equal to or less than a predetermined value. a transfer control unit that instructs the preemption control unit to prefetch the next channel command word at a low priority level when the value is larger than the value, and at a high priority level when it is smaller than the value; has.

[For production]

A comparator compares the byte count of the pre-empted CCW with a predetermined value, and if the byte count of the CCW is equal to or greater than that value, it is given a low priority level, and if it is small, it is given a high priority level. Since the next CCW is pre-fetched at the channel level, when unnecessary continuous operation of the device or high-speed processing is required, interrupts from sources other than the relevant channel can be avoided, reducing the occurrence of data overruns.

C Embodiment] - Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of a channel control device of the present invention.

This channel control device 2 is connected to the main storage device 1,
It controls a plurality of channel devices 101 to 10n, and is composed of a preemption area 3, a comparator 4, a preemption priority flip-flop group 5, a preemption control section 6, an interrupt control section 7, and a transfer control section 8.

Preemption area 3 is for each channel device 10. It has an area corresponding to ~lOn, and the CCW prefetched from the main storage device 1 is stored in the area corresponding to the channel device concerned. The comparator 4 compares the CCW byte count read from the main memory 1 with a predetermined value, and when the byte count value is equal to or larger than the predetermined value, the comparator 4 outputs "0". When it is small, it outputs "1". The first priority flip-flop group 5 is the channel device 1
It consists of flip-flops corresponding to 01 to 10n, and the comparison result by the comparator 4 is set in the corresponding flip-flop. The pre-fetch control unit 6 performs CCW pre-fetch processing and stores the CCW read from the main storage device in the pre-fetch area 3 corresponding to the channel device concerned. The interrupt control section 7 receives interrupt requests for data transfer from the channel devices 10, .about.10n, and instructs the transfer control section 8 to perform a transfer operation. The transfer control unit 8 creates data transfer information based on the CCW from the main storage device 1 or the prefetch area 3, and transmits the data transfer information to the corresponding channel devices 101 to 10. to instruct data transfer, and at the same time set the CCW data chain flag (not shown).
When it is determined that there is a data chain instruction, the preemption control unit 6 is instructed to prefetch the CCW. When the transfer control section 8 receives an interrupt request from the channel devices 101 to 10n and receives a transfer operation instruction from the interrupt control section 7, the transfer control section 8 extracts the preemption CCW from the preemption area 3 and transfers it to the corresponding channel device 10. ~
n as data transfer information, and when the data chain flag of the sent CCW is determined and the data chain is instructed, the comparison result by the comparator 4 stored in the preemption priority flip-flop group 5 is "0". When it is "1", it is a low priority level, and when it is "1", it is a high priority level and the next CC is
The preemption control unit 6 is instructed to perform preemption processing for W.

Next, the operation of this embodiment will be explained.

When the CCW is prefetched by the prefetch control unit 6, the comparator 4
compares the byte count of the prefetch CCW with a predetermined value. If the comparison result of the comparator 4 is that the byte count of CCW is equal to or larger than the predetermined value, "0" is set in the flip-flop of the corresponding channel device in the preemption priority flip-flop group 5, and if the byte count is small, "0" is set. "l" is set. Next, channel device 1
0°~. When a pre-emption CCW is sent to the request destination due to an interrupt request from a client, the transfer control unit 8 stores "0" in the corresponding flip-flop of the pre-emption priority flip-flop group 5 if there is a data chain instruction for this CCW. When "1" is stored, the preemption control unit 6 performs preemption processing for the next CCW with low priority, and with high priority when "l" is stored.

[Effects of the Invention] As explained above, the present invention compares the byte count of the preempted CCW with a predetermined value when prefetching a CCW in a channel control device, and determines whether the byte count is equal to or below the predetermined value. By pre-empting the next CCW with low priority if it is larger than the value and with high priority if it is smaller, unnecessary continuous operation of the device and interrupts from other channels are avoided when high-speed processing is required. This has the effect of reducing the occurrence of data overruns and improving the usage efficiency of the system as a whole.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of a channel control device of the present invention. l...Main storage device, 2...Channel control device, 3...Preemption area, 4...Comparator, 5...Preemption Priority flip-flop group, 6
... Preemption control section, 7 ... Interrupt control section,
8...Transfer control unit, 10+, +02,..., 10n...
Channel device.

Claims (1)

[Claims] A channel control device connected to a main storage device and controlling a plurality of channel devices, the device having an area corresponding to each channel device, and storing channel command words prefetched from the main storage device. A comparator that compares the prefetch area to be read, a byte count of the channel command word read from the main memory and a predetermined value, and a plurality of flip-flops corresponding to each channel device. a pre-emption priority flip-flop group that stores the comparison results of the pre-emption priority flip-flops; a pre-preemption control unit that pre-fetches a channel command word from a main memory and stores the channel command word in an area corresponding to the channel device in the pre-fetch area; An interrupt control unit that accepts a data transfer interrupt request from a channel device, and creates data transfer information using a channel command word read from the main storage device and sends it to the channel device, and creates a data chain of the channel command word. When a data chain is instructed by determining the flag, instructing the preemption control unit to prefetch a channel command word;
When a transfer instruction is received from the interrupt control unit in response to an interrupt request from each channel device, a preemption channel command word is extracted from the preemption area and data transfer information is sent to the channel device. If the data chain flag of indicates a data chain, the flip-flop corresponding to the channel device in the preemption priority flip-flop group is set to a state where the byte count of the channel command word is equal to or less than a predetermined value. a transfer control unit that instructs the preemption control unit to prefetch the next channel command word at a low priority level when the value is larger than the value, and at a high priority level when it is smaller than the value; a channel control device having a