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Hardware-Controlled I/O Function for a Twinaxial Work Station Controller

IP.com Disclosure Number: IPCOM000119567D
Original Publication Date: 1991-Feb-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 8 page(s) / 305K

Publishing Venue

IBM

Related People

Dancker, GA: AUTHOR [+3]

Abstract

A twinaxial (5250 protocol) Work Station Controller (WSC) would typically set up a single I/O operation (i.e., screen write) or a single queue load (series of commands) to one Work Station (WS). The WSC Licensed Internal Code (LIC) would wait for this operation to complete, check if any errors occurred, and then set up the next I/O operation. This article describes a hardware design that allows setting up multiple I/O operations to many WSs. An interrupt can be set at the end of any particular I/O operation in a string or when all I/O operations on a string complete. This allows the WSC microprocessor to be doing other work while the hardware is handling the I/O operations.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 22% of the total text.

Hardware-Controlled I/O Function for a Twinaxial Work Station Controller

      A twinaxial (5250 protocol) Work Station Controller (WSC)
would typically set up a single I/O operation (i.e., screen write) or
a single queue load (series of commands) to one Work Station (WS).
The WSC Licensed Internal Code (LIC) would wait for this operation to
complete, check if any errors occurred, and then set up the next I/O
operation. This article describes a hardware design that allows
setting up multiple I/O operations to many WSs.  An interrupt can be
set at the end of any particular I/O operation in a string or when
all I/O operations on a string complete.  This allows the WSC
microprocessor to be doing other work while the hardware is handling
the I/O operations.

      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 I/O chain function.

      The following list describes the control block formats for the
I/O function.  There are 16 bytes of information associated with each
control block. A graphical representation of each format that can be
used with the I/O chain is given in Figs. 1 through 6.  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 together before the
programmer issues a command to the WSC adapter logic.  The associated
internal registers must be set up...