TBBS 2.2 - Disabling Ports on 16-Port DigiBoards

Contact:   eSoft, Inc. (Makers of TBBS)
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DISABLING PORTS ON 16-PORT DIGIBOARDS
-------------------------------------

INTRODUCTION

In rare cases, it is possible for a port address conflict to occur when using 
16-port DigiBoard cards.  The greater the number of lines in use, coupled with 
more complex configurations (LAN cards, SCSI cards, etc. installed on the TBBS 
machine), the greater the chance for a conflict to occur.  This Tech Note 
deals with the address conflict issue. 

IN CASE OF CONFLICT...

If a DigiBoard port has a base I/O address conflict with another hardware
device, the line will fail to operate properly.  

Since the 16-port DigiBoard cards do not have configurable addressing (the 
addresses are burned into the PAL chips on the card) the best solution is to 
move the address of the conflicting device.  Most hardware devices which use 
base I/O addresses have jumpers or switches which allow address selection.  
Simply compare the possible address settings of the device with the list of 
addresses used by your DigiBoard cards, and move the address to one not in use 
by the DigiBoard. 

IF THE ADDRESS CANNOT BE CHANGED...

If the address of the conflicting device cannot be changed, there is no choice 
but to disable the DigiBoard port.  This will reduce the maximum numbers of 
lines you can run by one line for each conflicting port address.  

To disable a port on the DigiBoard and resolve the conflict, you need to 
remove one of the PAL chips, bend upwards one pin on the chip, and replace the 
PAL chip in its original location.  There is one pin for each address on the 
chip as follows: 

PAL Chip in Socket U58

Pin 23 = Port 1
Pin 22 = Port 2
Pin 21 = Port 3
Pin 20 = Port 4
Pin 19 = Port 5
Pin 18 = Port 6
Pin 17 = Port 7
Pin 16 = Port 8

PAL Chip in Socket U46

Pin 23 = Port 9
Pin 22 = Port 10
Pin 21 = Port 11
Pin 20 = Port 12
Pin 19 = Port 13
Pin 18 = Port 14
Pin 17 = Port 15
Pin 16 = Port 16

To identify the pins, hold the chip vertically with the small indentation at 
the top, pins facing down (away from you), like this: 

     +----v----+
  1 -|         |- 24
  2 -|         |- 23
  3 -|         |- 22
  4 -|         |- 21
  5 -|         |- 20
  6 -|         |- 19
  7 -|         |- 18
  8 -|         |- 17
  9 -|         |- 16
 10 -|         |- 15
 11 -|         |- 14
 12 -|         |- 13
     +---------+

Once you have identified the pin associated with the conflicting port, 
carefully remove the chip, noting the direction in which it is inserted.  
Using a pair of needle-nose pliers or a small screwdriver, carefully bend the 
affected pin upwards to be horizontal with the top surface of the chip.  The 
object is to ensure that the pin no longer makes contact with the socket when 
replaced. 

Replace the chip, making sure to position it in the same direction it was in 
when removed.  THE CHIP WILL BE PERMANENTLY DAMAGED IF INSERTED UPSIDE-DOWN! 

Once the pin is bent and the chip replaced, you need to modify your port 
configuration with CEDIT.  NOTE:  THE LINE SHOULD STILL BE DEFINED IN CEDIT	IN 
ITS PROPER LOCATION OR TBBS WILL NOT OPERATE IN EFFICIENT PORT HANDLING MODE!  

Change the affected port/line definition to be one of the two Autobaud "modem" 
selections.  Make sure Hard Wired=Y.  Having Autobaud selected and hard wired 
ON will allow TBBS to ignore the fact the port hardware is no longer valid for 
this port. 

- END -
TBBS0003
Rev. 10/93

Copyright (C) 1994 eSoft, Inc., All Rights Reserved.  Permission granted
to distribute this file in its entirety, without modification, to any
interested party.  Any other use requires the written permission of
eSoft, Inc.

IMPORTANT:  The information herein is subject to change without notice.
Please call or write to confirm factual information of importance to you
or your organization.

