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Hardware-Controlled Auto-Poll Function for a Twinaxial Work Station Controller

IP.com Disclosure Number: IPCOM000119571D
Original Publication Date: 1991-Feb-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 8 page(s) / 316K

Publishing Venue

IBM

Related People

Dancker, GA: AUTHOR [+3]

Abstract

A twinaxial (5250 protocol) Work Station Controller (WSC) needs to poll Work Stations (WSs) periodically to check if a key has been pressed, if status has changed, or if an error occurred. This would typically be controlled by the Licensed Internal Code (LIC). The LIC would set up each poll and also check every response for a new keystroke, status change, or an error. On the average, 90 percent of the polling is nonproductive, i.e., no key has been pressed, no status changed, or no error occurred. This article describes a hardware design that automatically polls WSs and only interrupts the WSC microprocessor when a new keystroke, status change, or error occurs. This allows the WSC microprocessor to be doing other work while the hardware is handling the polling.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 21% of the total text.

Hardware-Controlled Auto-Poll Function for a Twinaxial Work Station
Controller

      A twinaxial (5250 protocol) Work Station Controller (WSC)
needs to poll Work Stations (WSs) periodically to check if a key has
been pressed, if status has changed, or if an error occurred.  This
would typically be controlled by the Licensed Internal Code (LIC).
The LIC would set up each poll and also check every response for a
new keystroke, status change, or an error.  On the average, 90
percent of the polling is nonproductive, i.e., no key has been
pressed, no status changed, or no error occurred.  This article
describes a hardware design that automatically polls WSs and only
interrupts the WSC microprocessor when a new keystroke, status
change, or error occurs.  This allows the WSC microprocessor to be
doing other work while the hardware is handling the polling.

      The twinaxial WSC described in this article can attach up to 56
Work Stations (a Work Station can be a display, printer, or PC).  The
WSC twinaxial adapter logic design has two control block chains (one
auto poll and one I/O) as well as timers.  This function is utilized
by properly loading the necessary internal registers and issuing the
desired command.

      The control blocks reside in the WSC storage and 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 twinaxial adapter logic "reads" the control blocks, and
performs these operations to the attached work stations.

      All work station polling is handled on the auto poll 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 this happens, the WSC adapter logic will
automatically stop processing that control block on following cycles
of the chain.  Once this chain is started, the WSC adapter logic will
continue to cycle through it each time the auto poll delay timer
expires.

      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.

      This article will describe the Auto Poll chain function.

      The following list describes the control block formats for the
Auto Poll function.  There are 16 bytes of information associated
with each control block.  A graphical representation of each format
that can be used with the Auto Poll chain is given in Figs. 1, 2,
3 and 4.  All control blocks must start on a 16-byte boundary (the
low-order 4 bits must be zero) and must be located in the lowest one
Mbyte of storage.  The control blocks are set up in memory and
chained t...