Browse Prior Art Database

RCCU Modified Protocol

IP.com Disclosure Number: IPCOM000122490D
Original Publication Date: 1991-Dec-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 3 page(s) / 81K

Publishing Venue

IBM

Related People

Kawashima, K: AUTHOR [+2]

Abstract

Described herein is RCCU (Remote Channel to Control Unit) modified channel extend protocol which provides transparency of the control unit's initial status without interlocking.

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

RCCU Modified Protocol

      Described herein is RCCU (Remote Channel to Control Unit)
modified channel extend protocol which provides transparency of the
control unit's initial status without interlocking.

      An RCCU connection sample is shown in Figure 1.  The RCCU
channel extends the protocol (original) of the ISS (Initial Selection
Sequence) portion shown in Figure 2.
      The RCCU original ISS protocol:
      1. Host processor starts ISS.
      2. Local RCCU responds with CCR status.
      3. Local RCCU sends ISS information frame to remote RCCU.
      4. Remote RCCU starts ISS to a control unit.
      5. Remote RCCU gets real initial status from the control unit.

      If the real initial status from the control unit is one of an
accept status without any error status, this protocol can proceed
normally.

      If the real initial status from the control unit contains any
error status in it, condition unmatching occurs between the host
processor and the remote attached control unit.

      Once the host processor receives the CCR status as an initial
status, it is recognized as an 'Accept' condition, but actually the
remote attached control unit did not accept the ISS yet.

      Such a situation can be expected under the following
conditions:
  - Pending status exists at the control unit
  - Status change
  - Stacked status pending
  - Attention collision
     - Not ready for ready transition
     - Enter key hit

      The host processor...