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Browse Prior Art Database

Adaptive High Speed Sending Protocol

IP.com Disclosure Number: IPCOM000106118D
Original Publication Date: 1993-Sep-01
Included in the Prior Art Database: 2005-Mar-20
Document File: 6 page(s) / 179K

Publishing Venue

IBM

Related People

Booth, R: AUTHOR [+7]

Abstract

This article describes a method for use in a personal computer (PC) to transfer data to a remote device connected to the parallel port that would be capable of adjusting the transmission rate to the speed of the device connected to it.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 48% of the total text.

Adaptive High Speed Sending Protocol

      This article describes a method for use in a personal computer
(PC) to transfer data to a remote device connected to the parallel
port that would be capable of adjusting the transmission rate to the
speed of the device connected to it.

      The remote device can be any device that connects to the
parallel port, such as a printer, a scanner, or a PC.  The
transmitting device can be any device that is capable of transmitting
data via the parallel port, such as a PC or a bi-directional printer.
The transmitting device is hereinafter referred to as the "system."
A brief description of the signals involved in these transfer
follows:

-ACK
Data acknowledge.  This an active low signal that is used to indicate
that the remote device has received a byte of data.  During
transmissions to the remote device the leading edge of this signal
indicates that the remote device has received the byte and the
trailing edge of this signal indicates that the remote device has
processed this byte.  This signal is connected to pin 10 of the 25
pin parallel port connector.

+BUSY
Device busy.  This is an active high signal that indicates that the
remote device is not ready to receive data.  This signal is connected
to pin 11 of the 25 pin parallel port connector.

-STROBE
Data strobe.  This is an active low signal that indicates that the
data on the data lines is valid.  This signal is connected to pin 1
of the 25 pin parallel port connector.

DATA1-8
8 bit data bus used to communicate with the remote device.  These
signals are connected to pins 2-9 of the 25 pin parallel port
connector.

      Following is a description of the flowchart of the adaptive
high speed sending protocol which can be seen in Fig. 1.

1.  If the remote device has processed all previous bytes (i.e.,
    -ACK=1) and is ready for the next transfer (i.e., +BUSY=0) the
    system will load data onto the data bus once it becomes
    available.

2.  After waiting the data setup time the system will activate strobe
    (-STROBE=0) to inform the remote device that the data is valid.

3.  If the remote device is capable of high speed transmissions then
    strobe will be deactivated as soon as the remote device receives
    the data (as soon as -ACK=0).

4.  If the remote device is capable of receiving high speed
    transmissions but does not receive the data before the end of the
    strobe hold time the system will deactivate strobe and wait until
    the byte is received before changing the data.

5.  After the remote device receives the byte (i.e., -ACK=0), the
    system will load the next byte onto the data lines and wait 400ns
    setup time.

6.  Upon completing the setup time the system will activate strobe as
    soon as it verifies that the remote device has completed
    processing the previous byte and is ready for the next transfer
    (i.e., -ACK=1 and BUSY=0).

7.  If the remote dev...