Browse Prior Art Database

I/O Chain - Auto Poll Chain Timer for Work Station Controllers

IP.com Disclosure Number: IPCOM000102459D
Original Publication Date: 1990-Nov-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 3 page(s) / 139K

Publishing Venue

IBM

Related People

Dancker, GA: AUTHOR [+4]

Abstract

Some twinaxial (5250 protocol) Work Station Controllers (WSCs) contain an I/O Control Block chain and an Auto Poll (AP) Control Block chain. Keystroke polling is done with the AP chain; I/O operations (i.e., write to screen) are done with the I/O chain. If a long chain of I/O operations is running, the AP chain might not be accessed for hundreds of milliseconds, which could result in very poor keystroke performance. This disclosure describes a hardware design that allows the AP chain to interrupt the I/O chain. When the AP chain completes, the I/O chain resumes where it was interrupted.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 44% of the total text.

I/O Chain - Auto Poll Chain Timer for Work Station Controllers

       Some twinaxial (5250 protocol) Work Station Controllers
(WSCs) contain an I/O Control Block chain and an Auto Poll (AP)
Control Block chain.  Keystroke polling is done with the AP chain;
I/O operations (i.e., write to screen) are done with the I/O chain.
If a long chain of I/O operations is running, the AP chain might not
be accessed for hundreds of milliseconds, which could result in very
poor keystroke performance.  This disclosure describes a hardware
design that allows the AP chain to interrupt the I/O chain.  When the
AP chain completes, the I/O chain resumes where it was interrupted.

      The AS/400* twinax WSC supports up to 40 work stations (a work
station can be a display, printer, or PC).  The current WSC twinax
adapter logic design has two control block chains, one Auto Poll (AP)
and one I/O, as well as timers.  Polling is done with the AP chain;
I/O operations (i.e., write to screen) are done with the I/O chain.
This function is utilized by properly loading the necessary internal
registers and issuing the desired command.  It is designed with a
polling interrupt structure.  When an interrupt condition occurs, the
Interrupt Request line will be activated to the processor on the WSC
and internal status bits will be set.  This line will remain active
until the status bits have been masked off.

      The control blocks indicate the work station port and station
address, transmit or receive operation, byte count, etc., and are
accessed via Direct Memory Access (DMA).  The WSC twinax adapter
logic "reads" the control blocks, and performs these operations to
the attached work stations.

      All work station polling is handled on the AP chain and
requires little processor intervention after the chain is set up in
the WSC storage.  Only when a scan code returns (i.e., someone
presses a key on the keyboard) or an error occurs, will an interrupt
be posted.  When an interrupt is posted, the WSC adapter logic will
automatically stop processing that control block on following cycles
of the chain.  Once the AP chain is started, the WSC adapter logic
will continue to cycle through it each time the auto poll delay timer
expires.  The auto poll delay timer is a programmable timer for
selecting the time interval for polling work stations.

      The I/O chain can be used for polling but is architected for
transmitting large blocks of data.  The I/O chain is interrelated
with the I/O timer.  When a Start I/O (SIO) command is issued, the
chain will remain pending until the I/O timer expires.  This chain
must be started each time it is to be executed.  An interrupt is
activated to the processor on the WSC upon completion.  The status of
the execution is placed in the control blocks for the WSC Licensed
Internal Code (LIC) to inspect and take appropriate action.

      If a long I/O chain is executing, the current WSC design did
not all...