MiniSport Laptop Hacker - Vol 19.  Jan 1994 
To discourage pecuniary interests, Copyright (c) 1993 Brian Mork 
 
>>> ADMIN 
Remember, you can get copies on disk of any software or text file I re- 
fer to (including the MLHacker series) by sending me a disk and SASE. 
I'll put a variety of other MLHacker related goodies on there, too. 
Alternately, you may make a direct call to the data number listed below. 
In this case, use the FILES command, and L)og into the \public\computer 
directory. 
 
MLHacker is starting to show up on some Internet servers.  Ask around or 
you can offer to upload it for me to your nearest host. 
 
>>> PARALLEL PORT POTENTIAL 
The August 1993 (Issue #37) issue of Circuit Cellar INK has a six page 
article describing how to turn the PC parallel port into a powerful TTL 
input/output port, even if it's inherently only an output port (prior to 
the proliferation of PS/2 compatible bidirectional parallel ports).  The 
circuit uses only five chips: 2x 74LS374, 2x 74LS244, and 1x 74LS138.  I 
will eventually build one and report on some fun things to do with it, 
but in the meantime, I thought I'd give a pointer to the article to oth- 
ers in the crowd who could use this capability now. 
 
>>> 2ND MEGABYTE ADDITIONS 
Thanks to Griff, Troy, and Jeff.  Each has experimented around with the 
empty sockets in ZL-1s that hold a second megabyte of memory in ZL-2s. 
Bottom line is that you can add a standard IBM PC SIPP (1Mx9) or a Mac- 
Intosh type (1Mx8) memory package.  If you have SIMMs, you'll have to 
add some pins, and in some cases, trim the circuit board card to fit in 
side the Minisport case.  In all cases, you'll have to bend the package 
of memory over sideways after soldering it in.  Yea!  Anybody have some 
spare memory they'd like to sell me?  The "old fashioned" slow memory 
would work fine in this computer. 
 
>>> PACKET CONVENIENCE UTILITY 
I bet most of us use our Minisports for packet at one time or another. 
Here's a utility I recently wrote to fix an annoying problem.  The com- 
puter and the TNC are doing what they're suppose to, but that's not what 
I wanted!  The limited storage of the Minisport's RAM disk prompted me 
to do this one in assembly language.  You may have seen it on the nets 
as a stand-alone message.  As a special addition to MLHacker readers, 
the source code is included prior to the text of the other message. 
 
; PK232DMP, initiated Jan 94, BjM (Opus-OVH) 
; 
  XOR AH,AH 
  MOV AL,1      ; COMx -- put 1,2,3, or 4 here 
  PUSH AX 
  ADD AL,030    ; Convert COM number into ASCII 
  MOV [FILL],AL ; Create output message 
  POP AX 
  SUB AL,1 
  SHL AL,1 
  MOV BX,AX     ; COM address offset into BX 
  MOV AL,040 
  MOV ES,AX     ; BIOS Data Area Segment 
  MOV AX,ES:[BX]; Snag COM base from DOS table of addresses 
  ADD AL,4      ; Generate BASE+ModemControlRegister 
  MOV DX,AX     ;  put it into DX 
  IN AL,DX      ; Get existing Modem Control Register 
  OR AL,3       ; Set DTR and RTS true, and.. 
  OUT DX,AL     ;  rewrite to hardware 
  MOV AH,09     ; Select DOS "String->Std Output" function 
  MOV DX,STRING ; DS set by MSDOS prior to entry 
  INT 021 
  MOV AH,04C    ; MSDOS Program Termination 
  INT 021 
STRING: DB 'DTR and RTS on COM' 
FILL:   DB '  set true.$' 
 
Whenever I exited my TNC communication program and did other things with 
the computer, my PK232 continued to monitor the airwaves and eventually 
the text buffer filled up.  At this point, it would accept no new con- 
nects to its built-in mailbox, would stop monitoring traffic, and would 
log no new callsigns.  I wrote this short program to set DTR and RTS 
true on the PC compatible COM port connected to my PK232.  Now, I exe- 
cute the communication program (I use TPK) from within a batch file and 
execute this file from the same batch file after the main program ends. 
The PK232 thinks the comm program is still monitoring and it continues 
to send stuff the computer, keeping its internal buffer empty. 
 
----- cut here ----- 
e 0100 
32 E4 B0 01 50 04 30 A2 3D 01 58 2C 01 D0 E0 8B 
e 0110 
D8 B0 40 8E C0 26 8B 07 04 04 8B D0 EC 0C 03 EE 
e 0120 
B4 09 BA 2B 01 CD 21 B4 4C CD 21 44 54 52 20 61 
e 0130 
6E 64 20 52 54 53 20 6F 6E 20 43 4F 4D 20 20 73 
e 0140 
65 74 20 74 72 75 65 2E 24 
r cx 
0049 
n pk232dmp.com 
w 
q 
----- cut here ----- 
 
Cut out the 15 lines between the "cut here" lines and put them all by 
themselves into a file called INPUT.DBG.  Use the MSDOS DEBUG program to 
generate an executable .COM file using the command: 
 
C:> DEBUG <INPUT.DBG 
 
A bunch of stuff will scroll across the screen.  When it finishes, there 
will be a 73 byte file called pk232dmp.com in the default directory. 
Type "pk232dmp" on the command line to execute this program. 
 
Another COM port may be selected by changing the fourth byte (currently 
01) to another COM number, up to 04.  For example, if you want to access 
COM3, you would change ...E4 B0 01... to ...E4 B0 03... and then run 
debug to generate another copy of pk232dmp.com.  No provision is made to 
accept a command line input of COM port number in order to keep the pro- 
gram very small.  Perhaps you could make several copies called 
dump1.com, dump2.com, etc. 
 
>>> CROSSFLOW 
Troy says he has an EPROM burner that he can make copies of ROMs with. 
Rather than blithely throwing out his e-mail address, let me know if he 
could help you. I'll pass your name on and let him get hold of you.  At 
least one person has experienced sector errors on disk C: as a result of 
the built-in ROM going bad.  It's a standard chip, so copying someone 
else's and replacing yours should offer no technical trouble.  Is any- 
body out there brave enough to hack out the format of the ROM disk and 
tell me how to replace some of the MSDOS 3.0 distribution files with my 
personal files?  Now that would be sweet!  Power up the Minisport and 
have my own programs in ROM.  Leaves extra room on the ROM disk, too. 
Maybe my next project... after the laser radar.  See 'ya next month! 
 
Please provide feedback!      * Direct data 1-509-244-9260 
                              * AX.25 KA9SNF@wb7nnf.#spokn.wa.usa 
                              * Internet bmork@opus-ovh.spk.wa.us 
73, Brian                     * 6006-B Eaker, Fairchild, WA 99011 
