Browse Prior Art Database

Multiple Data Transfer Request

IP.com Disclosure Number: IPCOM000048845D
Original Publication Date: 1982-Mar-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 2 page(s) / 69K

Publishing Venue

IBM

Related People

Havelock, GW: AUTHOR [+2]

Abstract

When data is transferred to or from I/O device 100 (Fig. 1), the data is first stored in data storage 60 of I/O controller (IOC) 50. If data is being transferred from I/O device 100 to channel 30, the microcode of IOC 50 requests a channel transfer and the channel interface circuitry 55 transfers the data from data store 60 to channel 30. After a block of data has been transferred from data store 60 to channel 30 the microcode of IOC 50 must check the status of that transfer. If I/O device 100 has transferred another block of data into data storage 60, the microcode of IOC 50 would request another data transfer to channel 30. The data transfer arrangement just described is effective, but there is a burden of having the microcode check the status of the completed transfer and setting up and requesting the next data transfer.

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Multiple Data Transfer Request

When data is transferred to or from I/O device 100 (Fig. 1), the data is first stored in data storage 60 of I/O controller (IOC) 50. If data is being transferred from I/O device 100 to channel 30, the microcode of IOC 50 requests a channel transfer and the channel interface circuitry 55 transfers the data from data store 60 to channel 30. After a block of data has been transferred from data store 60 to channel 30 the microcode of IOC 50 must check the status of that transfer. If I/O device 100 has transferred another block of data into data storage 60, the microcode of IOC 50 would request another data transfer to channel 30. The data transfer arrangement just described is effective, but there is a burden of having the microcode check the status of the completed transfer and setting up and requesting the next data transfer. The present arrangement eliminates the need for microcode intervention between transfers of blocks of data. With the present multiple request mode operation as illustrated in Fig. 2b, there is no delay between data transfers which exists in the prior arrangement as illustrated in Fig. 2a.

In the multiple channel request mode the microcode of IOC 50 sets up the channel interface before requesting the data transfers. The microcode loads the number of data transfers to be requested into transfer number register 70 (Fig.
3). The block size of the data transfer is then loaded by the microcode in channel control regist...