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Fault-Tolerant Switch Control Interface for Bit-Sliced Network

IP.com Disclosure Number: IPCOM000105814D
Original Publication Date: 1993-Sep-01
Included in the Prior Art Database: 2005-Mar-20
Document File: 4 page(s) / 126K

Publishing Venue

IBM

Related People

Atkins, MG: AUTHOR [+7]

Abstract

The Switch interfaces between Ports, which can be sources or destinations, and BSMs (Basic Storage Modules). This Switch Control Interface allows the use of multiple switch slices in order to achieve the required bandwidth (Fig. 1).

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Fault-Tolerant Switch Control Interface for Bit-Sliced Network

      The Switch interfaces between Ports, which can be sources or
destinations, and BSMs (Basic Storage Modules).  This Switch Control
Interface allows the use of multiple switch slices in order to
achieve the required bandwidth (Fig. 1).

      As a result, the amount of I/O from the Switch to the Port
increases as the slices increase.  In order to reduce I/O, no parity
is used on the control bus from the Switch to Port.  Instead, the
Port uses Redundancy Checking to detect errors.  If the controls from
each Switch slice do not match, no states change until all controls
agree.

      The basic interface control signals are shown in Fig. 2.

      These signals control four different types of operations:
Synchronous, Asynchronous, Fetch, and Store.

      The handshaking is similar across all four operations, but each
requires a slightly different handling of the controls.  The ROUTE
CODE contains routing information for the Switch, and ROUTE CD VALID
indicates when the ROUTE CODE contains valid data.

SYNCHRONOUS SIGNALLING

      The SOURCE Port requests a connection to a DESTINATION Port.
The SOURCE sends pages to the DESTINATION Port and then requests a
disconnect when the transmission is complete.

1.  The Port requests a connection by activating ROUTE CD VALID.
2.  When the path is available, the Switch grants the connection by
    activating CONNECT.
3.  When the Port sees CONNECT, it deactivates ROUTE CD VALID and
    sends data to the Switch.
4.  The Switch can make the Port pause on a page boundary by
    activating SW_HOLD.  The Port will hold the data until the HOLD
    goes away.
5.  When the transmission has been completed, the Port issues
    DISCONNECT which causes the Switch to deactivate CONNECT.
6.  The Port, seeing CONNECT drop, deactivates DISCONNECT.

ASYNCHRONOUS SIGNALLING

      When a port is not being used, or even when it has an active
ROUTE CD VALID but no CONNECT, the Port can be used as a destination.

1.  ASYNC CONNECT is set, indicating that this Port is a destination.
2.  If the buffer on the DESTINATION Port gets full, Port HOLD is
    activated telling the SOURCE Port to pause data transmission on a
    page boundary.
3.  When the DESTINATION Port's buffer is no longer full, Port HOLD
    is turned off and the SOURCE can continue to send data.
4.  After the data transmission is completed, the Switch drops ASYNC
    CONNECT on the DESTINATION Port.
5.  If the old DESTINATION Port has an outstanding ROUTE CD VALID,
    the Switch issued CONNECT and allows the Port to source the
    operation.

FETCH OPERATION

      A Port fetches data from a BSM.

1.  The Port activates BUSY.  If an asynchronous connection is not
    pending, the switch activates BUSY ACK to prevent any
    asynchronous connections from occurring.  (During this ti...