Browse Prior Art Database

Method for Providing Status Information in Micro Channel Computer Systems

IP.com Disclosure Number: IPCOM000120080D
Original Publication Date: 1991-Mar-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 5 page(s) / 189K

Publishing Venue

IBM

Related People

Bonevento, FM: AUTHOR [+4]

Abstract

Described is a method of utilizing a field within the termination status block (TSB) of MICRO CHANNEL*-equipped systems so as to provide status information for a subsystem control block (SCB) command utilizing an indirect list function.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 43% of the total text.

Method for Providing Status Information in Micro Channel Computer
Systems

      Described is a method of utilizing a field within the
termination status block (TSB) of MICRO CHANNEL*-equipped systems so
as to provide status information for a subsystem control block (SCB)
command utilizing an indirect list function.

      Typically, as scatter/gather lists are implemented within the
SCB structure, completion status must be handled for short and long
exceptions.  The concept described herein provides a method to handle
the completion status by enabling the host program to recover from a
terminated command which uses the indirect list function.  Fig. 1
shows the concept's format for the TSB.

      In determining how residual data exceptions are reported, the
architecture is concerned with two values when dealing with data
transfers. The first value is the number of bytes remaining in the
buffer area to be moved when an operation is terminated. This is
called the residual buffer count.  The second value provides the
address of the 32-bit area which contains the start of the data
buffer in use when the command was terminated.  This is called the
residual buffer address. When an SCB operation involving data
transfers terminates with an error, the architecture specifies the
storing of these two values so that the software can determine the
progress of the operation toward completion.  The setting of the bits
8 and 9 in the TSB Word 0 will indicate whether or not these values
are provided when the error is reported by the device.  Storing of
residual byte count and buffer address is the architected manner in
which data transfer progress is to be reported to the program.

      Exception status reporting for SCB commands involves the
reading of the interrupt status port (ISP) to determine that an SCB
interruption has occurred.  From that point a detailed analysis is
needed of the TSB associated with an SCB which has requested an
interrupt.  The program examines the detailed status stored in the
TSB for an SCB operation which has been completed and requested an
interrupt.

      The TSB residual buffer count (TSB words 2 and 3) is used when
there are a number of bytes remaining to be transmitted to or from
the buffer. The address can be found by using the address given by
the buffer address stored in the TSB, as shown in Fig. 1, words 4 and
5.  If no data from a buffer has been moved, the residual buffer
count will be the length of the buffer.  If all data in a buffer has
been moved, the value will be zero.  If the optional buffer address
field is present in the TSB, then this field will also be present.
The number of bytes remaining to be read, or written in the buffer,
will be located by the address given in the TSB buffer address in TSB
status words 4 and 5. This field must be provided when either a short
or long length exception is detected.

      A 32-bit address within the SCB, or the indirect list used to
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