Dec 312017
Texas ZModem file transfer program. External file protocol for communications programs without ZModem built-in. Similar to DSZ, bu smaller because only ZModem is included.
File TXZM230.ZIP from The Programmer’s Corner in
Category Communications
Texas ZModem file transfer program. External file protocol for communications programs without ZModem built-in. Similar to DSZ, bu smaller because only ZModem is included.
File Name File Size Zip Size Zip Type
TXZM.DOC 27277 8862 deflated
TXZM.EXE 48681 31074 deflated
TXZMDIAL.DIR 1399 639 deflated

Download File TXZM230.ZIP Here

Contents of the TXZM.DOC file


(c) 1991-94 Mike Dumdei, 6 Holly Lane, Texarkana Texas
North East Texas DataLink 1:3819/128
BBS (903)838-6713, Voice (903)838-8307

TXZM (Texas Zmodem 🙂 is a zmodem protocol that was developed
to demonstrate the speed and capabilities of the MCOMM C serial
communications library. The latest version of TXZM or MCOMM may
be obtained from N.E.T. DataLink by either logging in and
downloading or by file request of "MCOMM" or "TXZM". The
shareware version of MCOMM contains the TXZM shell in source form
and the low level Zmodem driver in library form. The complete
source code comes with the "Libs & Source" registered version of
MCOMM. Libraries for all memory models except for the BCC/TC
huge model come with the "Libs Only" registered version of MCOMM.
See the MCOMM order form for specifics on various options.


TXZM IS NOT PUBLIC DOMAIN however the executable version may
be distributed and used free of charge for non-commercial
purposes. If you intend to use TXZM commercially or in a
commercial environment and the program will be loaded or operated
on more than 3 systems ANYWHERE within the organization, you must
obtain a license.

The complete TXZM source code is provided as part of the
"Libs & Source" registered version of the MCOMM software package.
Linkable libraries are provided with the "Libs Only" registered
version of MCOMM. None of the source code or libraries that are
part of the registered version of MCOMM may be distributed,
neither may they be incorporated in whole or in part into a
competing software product without a written license agreement.
Competing software products are products that are not end user
programs themselves, such as "Your Serial Library", and products
that directly compete with TXZM (fully developed terminal
programs, BBS systems, and similar products are FUNCTIONALLY
DIFFERENT than TXZM and NOT considered competing products).

The license agreement requirement for commercial use of the
governmental, educational, church, civic, or non-profit
organizations. This does not waive restrictions that apply to
the source code for those organizations.


MCOMM is a serial communications library for Microsoft C,
Turbo C/C++, Borland C/C++, and Zortech C/C++. It also will work
with any other C compiler or language that supports Microsoft C
calling conventions. Some of the features of MCOMM are:

- Fully interrupt driven
- 16550 FIFO mode support
- Baud rates up to 115200 baud
- Supports definitions for any comm port that operates on
IRQs 2 through 7 at any address
- Supports simultaneous operation of 2 ports
- Written in assembler for maximum speed and minimum code
- Advanced features such as block transmit and receive,
XON/XOFF and hardware flow control, receive buffer look
ahead, definable ring buffer sizes and location, ...

Also included with MCOMM is a set of ANSI capable video
functions that support windowed output, save/restore screen
functions, timer functions, and miscellaneous other code. The
current shareware version of MCOMM is MCOMM557.ZIP. It includes
a complete small model LIB, TXZM (partial source, rest as libs),
and both a C and C++ demo terminal program. The registered
version is available as either "Libs only" or "Libs & Source".
The "Libs Only" version is $25 and includes libraries for all
memory models. The "Libs & Source" version is $45 and comes with
both libraries and all source code. See the MCOMM order form.


TXZM has 3 modes of operation. These are command line send,
command line receive, and terminal mode. Running TXZM with no
command line parameters will list available TXZM options.

Specifying the serial port:

TXZM directly supports COM1 through COM4, however COM3 and
COM4 on older hardware may not match what is considered
standard. The -c switch (described below) may be used for non-
standard configurations of COM3 and COM4 or to force TXZM to
recognize a custom port. For standard versions of COM1-4, use
"txzm com#" where '#' is 1-4.

TXZM switches:

-u Start in terminal mode. Terminal mode may be started
either before or after a CONNECT is made. It has a
limited set of functions (dial, upload, download).

-r Start in receive mode. This switch must come last on the
command line if it is used. It may be followed by an
optional subdirectory if the files are to downloaded to a
specific location. The -r switch may be used in
conjunction with the -u switch to specify a download
directory. When used with the -u switch, TXZM starts in
mini-terminal mode.

-s Start up in send mode. This must be the last switch on
the command line and be followed by the filename(s) to be
sent. The filename list may contain wild cards. The send
function will recurs subdirectories if the filename
specifications are placed in parenthesis. Placing
filenames in parenthesis to recurs subdirectories also
works in mini-terminal mode.

-p Send or accept complete pathnames. This option, used in
conjunction with the -r option, will cause TXZM to accept
complete pathname information in the received filename.
Without it, only the root name and extension of the
filename are used. If the received filename specifies a
directory that does not exist, it will be created. If a
download directory was specified (-r dlpath), the
subdirectories will be created under "dlpath".

When used with the -s switch, the -p switch will cause
filenames to be sent with complete path information. Per
zmodem specifications, only the path is sent (no drive
identifiers). Without the -p switch only the file's root
name and extension are sent. This applies even if
recursing subdirectories.

-b#### Specify the CONNECT baud rate. The CONNECT baud rate
is used to determine estimated file transfer times. TXZM
currently will not adjust to a CONNECT rate when
initially making the connection. Unless a locked baud
rate is used (-l), you must dial using the baud rate you
will CONNECT at. If the connection is already
established, and neither -l or -b is given, TXZM will
open the port using the baud rate it is currently
operating at.

-l#### Set a locked baud rate. Use this option to set a
fixed computer to modem baud rate. The -b option may be
used with the -l option to specify both the computer to
modem rate and the modem to line rate.

-chhh,# Specify a non-standard port configuration. TXZM
will work with any port addresfrom 000h to 3f8h and IRQs
2-7. Replace 'hhh' with the port address in hex and
'#'ith the IRQ to be used. For example, to use a port at
I/O address 2E8h that uses IRQ 5, use "txzm -c2E8,5".

-h Use hardware flow control (RTS/CTS). This is required
for modems that use a locked baud rate.

-i Ignore absence of carrier detect signal. Use this switch
when using TXZM to transfer files between systems
connected with a null modem cable. (TXZM only requires
the Rx, Tx, and Gnd wires to be connected).

-v Disable serial I/O during disk writes. Use this option
if errors occur when the received data is written to
disk. This should only be necessary when operating at
high baud rates with no 16550 UART or the file is being
downloaded to a floppy. The -v option also expands the
disk buffer to 20K bytes to maintain a higher level of

-e# Set duplicate file handling option. This option
determines what happens if an attempt is made to download
a file that already exists. The following choices are
-e0 Skip the file -- do not download.
-e1 Resume the transfer at the end of current file.
This is the default.
-e2 Create a duplicate file name and download the file
as a separate file.
-e3 Overwrite the existing file.

-w#### Sets the maximum bytes that may be in transit at any
one time (transmit window size). This must be a multiple
of 128.

-x Escape all control characters. This option causes the
characters between 00h and 20h, 80h and A0h, 7Fh, & FFh
to be ZDLE escaped. Zmodem automatically escapes XON,
XOFF, ZDLE (CAN), DLE, and "@" sequences. The -x
option is for networks that do not pass other control

-x# As an option, a specific list of control characters to
escape may be given. For example to only ZDLE escape the
ESC character (27 decimal or 1B hex) and ESC+parity (145
decimal or 9B hex) and let all other control characters
pass unaltered, use: -x27,145.

-6 Force use of 16 bit CRC. The default is 32 bit CRC. This
option does not show up on the help screen (ran out of

-7 Strip high bit from received characters in terminal mode.

-0 Use BIOS screen writes. This only works in command line
mode. Mini-terminal still does direct writes.

-q Run in DesqView mode. This option makes TXZM DesqView
aware meaning it writes to DesqView's video buffer rather
straight into video memory. It also causes TXZM to
release its time slice when it is idle.

-y Added in version 2.25. Allows overriding the received
filename on Zmodem receives. Ex:
txzm -y THISNAME.ZIP -r
The above line would cause the received file to be called
"THISNAME.ZIP" rather than the name sent by the sender.
This option does not show on the help screen.

-$ Added in version 2.30. Sets "quiet mode" when doing file
transfers. With this option set, the display of the
zmodem transfer screen and transfer stats are disabled.
This option does not show on the help screen.

16550 related switches:

-d Do not enable 16550 FIFO mode. Normally TXZM
automatically enables FIFO mode. If you are using a
Western Digital 16550 UART at lower baud rates you may
need to use this option. The WDC16550 UART doesn't work
in FIFO mode at low baud rates. If you have a 16550 and
don't know if it is a Western Digital but get Garbled
Packet errors when attempting to start a transfer, try
this option. The National Semiconductor 16550 (NS16550A)
works at all baud rates in FIFO mode.

-t# Maximum characters to send to 16550 FIFOs per interrupt.
This may be between 1 and 16. The default is 8. A lower
value may be required for modems that used a locked baud
rate, hardware flow control, and have a small internal
buffer. 8 works fine with USRs.

-m Disable modem status register interrupts. This option is
another patch to accommodate Western Digital's version of
the 16550. Some WDC16550s lock up if the modem status
lines (CTS, CD, etc.) are not connected to a driving
signal. This could happen if the serial or null modem
cable being used does not have all signal lines connected
(very possible with a null modem cable). Using -m
prevents this problem. It also disables hardware flow
control and carrier detect, however, so if you require
either of these and have a WDC16550 you must use a cable
with all appropriate lines connected.


txzm -p -s (c:\) // send all files on drive C -- include
// complete path information

txzm -p -r // accept complete pathnames -- if path
// does not exist, create it

txzm -p -r d:\temp // accept complete pathnames but put files
// and created directories under D:\TEMP

txzm -r // receive to current directory, if path
// information is received it is ignored

txzm -s (\project\*.c) (\project\*.h) // Sends all .c and .h
// files in the subdir PROJECT and all subs
// under project. Does not send pathnames.

txzm -u -r \dnlds // start in mini-terminal mode, received
// files are placed in "\dnlds" directory

txzm com2 -u // mini-terminal mode, use COM2

txzm -l38400 -b9600 -h -s
// 38400 baud locked rate, 9600 CONNECT,
// hardware handshake, send file list

txzm -b2400 -u // 2400 baud, mini-terminal mode

txzm -c2e0,7 -r // custom serial port at 2E0h on IRQ7,
// use current baud rate, receive

txzm com2 -b115200 i u // 115200 baud, ignore carrier detect,
// mini-terminal mode

txzm -e2 -r // COM1, current baud rate, receive, create
// duplicate name if file exists

txzm -s @filelist // send all files listed in "filelist"
// the name "filelist" is an example only

Other than the -r and -s switches that must appear last on the
command line if used, neither case nor switch order are significant.
Also you may use a '/' instead of a '-' or no switch identifier at
all. Ex: "txzm i E2 -u /b2400 r" is legal syntax.


TXZM is faster than any other zmodem protocol driver I am aware
of. It will run at 95% efficiency in both send and receive modes at
115200 baud on an 8 MHz 286 with a 16550 UART. This translates to an
effective throughput of 110 Kbps. In a PC Magazine (Apr 91) article
reviewing various communications software packages, the BEST zmodem
operated at less than 50 Kbps when tested at 115200 baud on the same
type of equipment (8 Mhz 286's with 16550 UARTs). TXZM is over twice
as fast. The review covered several well known shareware and
commercial packages.

TXZM was also tested on a 4.77 MHz 8088 laptop that contained the
functional equivalent of a 16450 UART (no FIFOs) and a 4.77 MHz IBM
XT (true blue IBM) that had 16550 UARTs installed. On the laptop
system TXZM could send most efficiently at 23040 baud and receive
most efficiently at 28800 baud. The XT, with 16550 UARTs, could
receive at a full 38400 baud but with the baud rate set to 38400
could only achieve an effective throughput rate of around 35000 baud.
The tests were performed using the systems' hard drives (original
slow hard drives), not a RAM disk, which also had some impact on
speed. With 16550 UART's, TXZM could very effectively work a high
speed modem (HST, V.32, or V.32bis) even on a slow 4.77 MHz computer.

If you compare the CPS rating stated by TXZM and other programs,
you may find TXZM reporting slightly lower rates. This is due to a
difference in the calculation method TXZM uses only. Many other
progams appear to fudge a little bit on their statistics. At lower
speeds or on fast CPUs all Zmodem drivers will run about the same.
The speed difference shows up when the system is under a load such as
with extremely high baud rates or moderately high baud rates on slow


TXZM now recognizes the TXZMLOG environment variable and will
create a log file with the same format as the one created by DSZ if
DSZLOG is set. This was added primarily to support BBS software that
uses DSZLOG format log files to track downloads, efficiency, etc. If
all you want is a log file you can set TXZMLOG only. If you are
using BBS software that looks for a DSZLOG variable, you will have to
also set DSZLOG to the same value as TXZMLOG. Ex:


I did not use DSZLOG to avoid infringing on any non-public domain
features of DSZ. If you want to patch your personal copy of TXZM to
use DSZLOG directly rather than TXZMLOG, you can use a utility such
as Norton Utilities or PC Tools to scan TXZM.EXE for the string
"TXZMLOG" and change it to "DSZLOG". This is only patch you are
authorized to make. DO NOT under ANY circumstances distribute ANY
modified version.

It is also now possible to specify a file that contains a list of
the files to be sent. This is also primarily for BBS support. To
use this option precede the file containing the list of files with an
'@' sign. The files may be separated by any valid whitespace
characters including spaces, tabs, carriage returns, line feeds, etc.

The -q option has been added as of version 2.10 for BBS operators
who run under DesqView. It causes TXZM to not mess up the video and
also to release CPU time when it is waiting for characters or for the
transmit buffer to empty.

The -0 option will disable direct screen writes if you are using
command line send or command line receive options. All screen writes
will be done through BIOS calls. Mini-terminal mode does direct
writes even with the -0 option specified. -0 does not appear on the
help screen.

BBS sysops may also use TXZM free (even if you charge for access
to your system).


2.30 Finalized version of the 2.26b. Also 1) modified the routine
that captures the CONNECT rate so that it works with the
higher speed modems (V.FAST), 2) added a "quiet mode" of
operation (see -$ flag) that disables the zmodem transfer
display screen, and 3) added the ability to specify a modem
init string and the dial prefix string via the TXZMDIAL.DIR.
See TXZMDIAL.DIR for more information.

2.26b Added an optional dialing directory for miniterm mode. The
dialing directory is an ASCII text file (you create) that
TXZM looks for when the program first loads (see TXZMDIAL.DIR
for an example of how to set up the directory). Also changed
the CPS calculation routine to make it display correctly
when running under DesqView. (THIS IS A BETA VERSION).

2.25 Fixed the "-c" (custom comport switch). Added -y (override
received filename) switch.

2.24 Fixed a problem with the "recurse subdirectories" option and
also corrected a problem that caused TXZM to not work right
when running it in a DOS box under OS/2.

2.22 Recompiled using a different version of the MCOMM communica-
tions driver.

2.21 Fixed a divide by zero error that occasionally occurred on
restarted file transfers.

2.20 Added support for Doorway mode (ALT = toggles it on and off).
Added support for BBSs that autodetect ANSI capable programs.
Added -7 switch to enable stripping high bit when in terminal

2.14 Minor changes so code will compile without warnings using
BC++ 3.0 and so that TXZM would automatically trigger a
Qmodem download (Qmodem requires an "rz\r" as well as the
INIT packet -- most programs trip on the INIT packet alone).
Also modified the -n (BBS support option) so that it took the
name of a Maximus or Opus style LASTUSER.BBS filename rather
than a node number. Modified FIFO usage so that TXZM set
FIFO buffers to 1 in terminal mode and 8 when sending files
(corrects jerky display at low baud rates).

2.10 Changed name to TXZM from ZMP. The ZMPLOG envrionment
variable is now TXZMLOG. Found out somebody else already had
a ZMP in CP/M days. Added DesqView aware option. Fixed Dial
Command so that it looked at the connect baud rate and
adjusted accordingly. Fixed Redial Command to continually
dial until a connect was made or ESC pressed. Added F1 for
help key. Added ALT-P so the modem parameters could be
changed manually, ALT-C so the screen could be cleared, and
ALT-= for Doorway mode operation.

2.00 First non-beta version. Added a capture file. Fixed a minor
problem with the -0 option.

1.21 Added support for specifying files to send in a file that
contains a list of the filenames. Added -0 option (disable
direct screen writes in command mode).

1.20 Fixed bug introduced in version 1.19 that caused a divide by
zero error if the total bytes to be sent was between 1 and
18. Added ZMPLOG environment variable.

1.19 Corrected bugs in the -w and -x options. Fixed problem with
negative CPS rates showing up when more than 11 megabytes
were sent. Added the -6 switch.

1.17 Fixed double backslash in pathnames when downloading while in
the root directory (couldn't DL to root).

1.16 Added support for send and receive of complete pathnames and
creation of subdirectories. This allows duplication of
entire drives or subdirectories through the serial port.

1.10 16 bit CRC mode now really does work. TXZM102 was supposed
to have fixed it but didn't.

1.02 Fixed bug in 16 bit CRC mode (I thought). Fixed minor error
in ZRPOS handler. The sender now sends a ZCRCW packet when an
error occurs rather than a ZCRCG. This conforms with Chuck
Forsberg's Zmodem specification.

1.01 Fixed bug in ZRPOS handler. This bug occasionally caused
TXZM to trash the screen and lock up when a ZRPOS was
Optimized the code. TXZM will now operate at 115200 baud at
95% efficiency on an 8MHz 286 (approx 11100 cps -- 2 meg in 3
mins). A 16550 UART is required to obtain high speed
In mini-term mode, PGDN puts TXZM in receive mode in case
the sender's ZRQINIT was missed. Previously it relied on the
incoming ZRQINIT to trigger receive mode. It now works
either way.
Added a '-v' switch. This switch disables overlaying disk
and serial I/O. It also expands the receive file buffer to
20K bytes. The result is 20K of data is received, serial I/O
pauses, the 20K is written to disk, a ZACK is sent, and the
sender resumes sending.

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