Browse Prior Art Database

Control Unit Simulation On the Serial Channel

IP.com Disclosure Number: IPCOM000120556D
Original Publication Date: 1991-May-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 3 page(s) / 130K

Publishing Venue

IBM

Related People

Casper, DF: AUTHOR [+4]

Abstract

Simulating Control Units on channels allows a complete system test of a Computer System without attaching I/O boxes or special test equipment to the system.

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

Control Unit Simulation On the Serial Channel

      Simulating Control Units on channels allows a complete
system test of a Computer System without attaching I/O boxes or
special test equipment to the system.

      On the Serial Channel, simulating a Control Unit is done by
adding some hardware and microcode.  The code analyzes message frames
sent by the channel to the Control Unit and generates response
message frames back to the channel.  A hardware data generator
generates predictable data patterns for the data being sent to the
channel on read commands.  The same data generator is used to check
data being received from the channel on write commands.
Added hardware to simulate a Control Unit.

      SIM I/O LATCH.  When the SIM I/O latch is active, the channel
is put in a mode of operation that allows it to simulate a Control
Unit.  The Channel's Outframe Trace Buffer becomes the SIM Control
Unit's Outframe Buffer.  In this mode of operation there is no
outframe trace.  The Channel's Outframe Header is also the Control
unit's Inframe Header buffer.  The paths that are shown in dashed
lines are enabled in the figure below.

      START FRAME LATCH.  When the microcode sets this latch, the
hardware transmits the data in the Channel's Outframe Buffer to the
serializer.  When the SIM I/O LATCH is active, the Start Frame Latch
does not cause the Outframe Buffer to be transmitted.  Instead it
causes a CONTROL UNIT INTERRUPT.

      CONTROL UNIT INTERRUPT.  This preemptive interrupt is used by
the SIM I/O code as initiative to look in the Channel's Outframe
Buffer, which is the SIM Control Unit's Inframe Buffer.  The Control
Unit code analyzes the message in the Control Unit's Inframe Buffer
and generates a response message in the Control Unit's Outframe
Buffer. When the Control Unit code does a SIM START FRAME the Control
Unit's Outframe Buffer is sent to the serializer by hardware and is
received by the channel into the Channel's Inframe Buffer.  The
Control Unit Interrupt can also be armed by the Control Unit code, so
that the interrupt can be reentered again when the current Control
Unit's frame has been sent to the channel by the hardware.  This is
used in data transfer when the Control Unit sends multiple frames to
the channel in response to one frame sent to the Control Unit by the
channel.

      The Control Unit Code is a separate piece of code that is
resident in the channel's writeable pageable section of control
store.  Whenever the Control Unit interrupt occurs, the channel
engine task switches to the Control Unit code. When the Control Unit
code task is completed a task switch returns control back to the
channel code.

      A fiber connecting the channel's transmitter back to the
channel's receiver, shown as a do...