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Browse Prior Art Database

PC 3270 Single-Port Controller

IP.com Disclosure Number: IPCOM000120638D
Original Publication Date: 1991-May-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 2 page(s) / 81K

Publishing Venue

IBM

Related People

Carissimo, DJ: AUTHOR [+3]

Abstract

The 3270 emulator card can be used as a single-port controller simply by changing the firmware used to run the microcontroller on the card. The card consists of a high-speed microcontroller, a data buffer memory, an instruction memory, a Personal Computer bus interface, and a 3270 coax cable interface.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

PC 3270 Single-Port Controller

      The 3270 emulator card can be used as a single-port
controller simply by changing the firmware used to run the
microcontroller on the card.  The card consists of a high-speed
microcontroller, a data buffer memory, an instruction memory, a
Personal Computer bus interface, and a 3270 coax cable interface.

      When the Personal Computer with the 3270 card is first powered
up, the firmware executed by the 8X305 microcontroller initializes
the card.  The initialization clears the buffer memory and the
dual-port register array which is used to pass parameters between the
PC and the microcontroller on the card.  The microcontroller then
waits until the PC is ready to start emulation by enabling the card.
This is done by setting a flag bit in the dual-port register array.

      The microcontroller then enters the Service Loop.  It tests the
Command register in the dual-port register array to see if PC wants
to talk to a device.  If not it enters the Poll Loop.

      In the Poll Loop, the firmware will place a Poll command in the
Transmit latch.  The serializer hardware will encode the parallel
data in the Transmit latch, add the appropriate check bits, and send
it serially out the coax line to a device.  The firmware will then
start the No Response timer.  The timer flags a No Response Timeout
if the cable has no device or a device that is powered off.  If a
device is active on the line, it will send back a Status in response
to the Poll.  This serial data will come back into the receiver.  The
receiver will convert the serial data into parallel and check it for
proper protocol.  If it was received correctly, it will load it into
the Receive Data latch.  If the response was Clean Status (all
zeroes) then the firmware will repeat the Poll...