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System Control Block Get Configuration Command

IP.com Disclosure Number: IPCOM000099993D
Original Publication Date: 1990-Mar-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 6 page(s) / 200K

Publishing Venue

IBM

Related People

Bonevento, FM: AUTHOR [+3]

Abstract

This article describes a technique which provides a means for a computer operating system to obtain the current configuration of functions supported by a subsystem.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 33% of the total text.

System Control Block Get Configuration Command

       This article describes a technique which provides a means
for a computer operating system to obtain the current configuration
of functions supported by a subsystem.

      Fig. 1 shows the Read Configuration command format for the
system control block (SCB) command.  This command has the attention
port set as indicated.  It is executed by the host program to
determine parametric data about the subsystem or the devices attached
to the subsystem.  The subsystem control block BASIC format for read
configuration is shown in Fig. 2.  The command must be capable of
being executed even if the device requires initialization using the
Initialize Device command.  The SCB command must contain a memory
address 2, which points to the read configuration status block, and
the byte count area, which gives the size of the read configuration
status block, as shown in Fig. 3. The byte count is greater than or
equal to 44 bytes.  The first 22 words of data are standard for all
devices.  Data beyond the first 22 words is device dependent.

      If the data area defined by memory address 2 is smaller than
the amount of data which the device intends to return, then a long
length record condition exists.  The condition will request an
interrupt if not suppressed in this SCB. Termination status block
(TSB) status including a residual byte count and buffer address are
always given when a long-length record condition exits.

      In the case of a long-length record condition, if the SCB
memory area 2 is defined to be at least 22 words in length, word 22
will contain a 16-bit value indicating the size of the remaining
device dependent data which was not transferred in this command.

      If the data area defined by memory address 2 exceeds the length
of the configuration data to be transferred by the device, a short-
length record condition exists.  The condition will request an
interrupt if not suppressed in the SCB.  TSB status, including a
residual byte count and buffer address, is given when a short-length
record condition exists.  On a short-length record condition, word 22
+44 gives the number of valid bytes returned.
     The addressed device must accept this command for execution even
if it is in a state where it requires initialization using an
Initialize Device command.
     The addressed device is accessed for its configuration data.
When the addressed device is address 0, the command is directed to
the subsystem.

      It should be noted that data transfer and exceptions are
performed exactly as defined in the read SCB command.

      The command is defined as follows:
1.   The addressed device must accept this command for execution even
if it is in a state where it requires Initialization using an
Initialize Device command.
2.   The addressed device is accessed for its configuration data.
When the addressed device is address O, the command is direc...