Browse Prior Art Database

Auto Poll Chain "Skip Count" Enhancement for Work Station Controller

IP.com Disclosure Number: IPCOM000119253D
Original Publication Date: 1991-Jan-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 3 page(s) / 108K

Publishing Venue

IBM

Related People

Dancker, GA: AUTHOR [+4]

Abstract

There are two types of polling: keystroke polling (ACK) and polling for a work station to finish processing a command (NAK). A skip count is used to adjust the time interval of keystroke polling. NAK polling rates are typically a 1 to 4 millisecond time interval between polls. Keystroke polling is done by using a multiplier (skip count) of the NAK rate (typically a 10 to 30 millisecond time interval between polls). The timer that enables the polling operations to take place can be held off by other operations. This delays the keystroke polling. Described is a hardware design that keeps a count of how many times the timer has decremented to zero (while it is being held off by another operation) and subtracts this value from the skip count. This improves keystroke handling and overall Work Station Controller performance.

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Auto Poll Chain "Skip Count" Enhancement for Work Station Controller

      There are two types of polling:  keystroke polling (ACK)
and polling for a work station to finish processing a command (NAK).
A skip count is used to adjust the time interval of keystroke
polling.  NAK polling rates are typically a 1 to 4 millisecond time
interval between polls.  Keystroke polling is done by using a
multiplier (skip count) of the NAK rate (typically a 10 to 30
millisecond time interval between polls).  The timer that enables the
polling operations to take place can be held off by other operations.
This delays the keystroke polling.  Described is a hardware design
that keeps a count of how many times the timer has decremented to
zero (while it is being held off by another operation) and subtracts
this value from the skip count.  This improves keystroke handling and
overall Work Station Controller performance.

      The Work Station Controller twinaxial adapter logic operates on
control blocks residing in memory which are pointed to by internal
registers.  These registers are initialized prior to issuing a
command.  The WSC adapter logic will then fetch the control blocks
(via DMA) and execute the commands in them.  There are two control
block chains:  an Auto Poll (AP) chain mainly for polling the Work
Stations, and an I/O chain mainly for I/O operations (i.e., write to
screen, read screen, etc.).

      The two chains interact in the following way:
1.  The AP chain has priority over the I/O chain whenever there is
contention.
2.  The AP chain becomes 'pending' when the AP command is issued and
the AP delay timer is zero.
3.  The I/O chain becomes 'pending' when the I/O command is issued
and the I/O timer is zero.
4.  If an I/O chain is executing, and an AP chain is pending, the AP
chain will begin execution and become active after the I/O chain
completes execution.
5.  If an AP chain is executing, and an I/O chain is pending, the I/O
chain will begin execution and become active after the AP chain
completes execution and the AP delay timer is not zero (i.e., AP
chain is not pending again).

      There are two types of polling:  keystroke polling (ACK) and
polling for a work station to finish processing a command (NAK).  A
skip count is...