Browse Prior Art Database

Processor To Processor Direct Memory Access Write in a Closed Ring Data Transmission Loop

IP.com Disclosure Number: IPCOM000052856D
Original Publication Date: 1981-Jul-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 2 page(s) / 13K

Publishing Venue

IBM

Related People

Darman, AP: AUTHOR [+2]

Abstract

A remote processor connected to a data transmission loop having multiple processors connected to it can place data into another processor's storage at a storage location specified by the remote processor. Implementation in the IBM Series/l data transmission loop environment required the addition of three I/O commands to the Series/1 channel command set: "non-specific read' to subchannel 1, "unsolicited data/data end' and "solicited data/data end' to subchannel 2. These are under control of modifier bits 8 through 11 of the device control block (DCB) control word. The standard data/data end and read commands remain unchanged in their definition and operation.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 53% of the total text.

Page 1 of 2

Processor To Processor Direct Memory Access Write in a Closed Ring Data Transmission Loop

A remote processor connected to a data transmission loop having multiple processors connected to it can place data into another processor's storage at a storage location specified by the remote processor. Implementation in the IBM Series/l data transmission loop environment required the addition of three I/O commands to the Series/1 channel command set: "non-specific read' to subchannel 1, "unsolicited data/data end' and "solicited data/data end' to subchannel 2. These are under control of modifier bits 8 through 11 of the device control block (DCB) control word. The standard data/data end and read commands remain unchanged in their definition and operation.

Two additional words are stored in the residual status block. One word contains a one-byte frame origin address and a one-byte storage protect key. The other word contains the data address. This allows the software to determine who the data is from and where it is located in its storage.

The non-specific read command, with DCB modifier bit 11 active, ignores the ring address in the DCB and, as a result, will accept any type of data/data end frame from any source. The timeout is suspended and the command will remain active until it is utilized or a reset has been issued either by software (device reset or halt I/O) or hardware (IPL or machine reset). A read ready is not transmitted as there is no known ring address to send it to. The origin address is extracted from the frame and placed in the ring address of the DCB.

When bit 0 of the frame control byte is active, "solicited data/ data end', the first four bytes of data, namely, the "destination header', are utilized as follows: ##

The remaining data in this frame will be stored starting at the location contained in the destination header.

After the first 1000 bytes are received by a...