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BlockTerm v6.0 is now available for download.
Please read the BlockTerm changelog for current BlockTerm development status.
- 5/12/13 - BlockTerm v4.4 introduced a new block format. This new format is not compatible with v4.2 or earlier.
- 10/25/13 - BlockTerm v5.0 corrects a fatal error in earlier versions. All users should upgrade to v5.0 or later.
- Current versions of BlockTerm require MS-DMT v1.00 Build 18.104.22.168 or later (available here) to operate correctly.
- Do not install BlockTerm until you have installed the new modem.
Already familiar with everything on this page? Download and install BlockTerm V6.0.
Want to receive an email when a new version is available? Just send an email to email@example.com.
Configuring your Computer for BlockTerm -
IMPORTANT! Read this entire page before starting.
Sometimes, when large messages are transmitted via M110A, the message is lost when the modem fails to retain synchronization.
Getting Started -
This can be caused by the lack of resynchronization data within the M110A specification. As sound card clocks drift ever so slightly,
clock error accumulates until synchronization can no longer be maintained. This can also be caused by poor propagation.
BlockTerm is designed to ameliorate the loss of synchronization by breaking large messages into small blocks and
sending all block with a small delay between them. This re-synchronizes the clock before each block making loss of
synchronization less likely. When all blocks have been received, the original message is reconstructed.
If a block is received with errors, the transmitting station, or any receiving station, can fill the block by retransmitting
just that one block.
BlockTerm communicates with the M110A Data Modem Terminal (DMT) by using a virtual COM port. A virtual COM port is a software
Installing com0com or VSP Manager -
program that allows applications to converse with each other as if they were connected by wires. This page will detail the configutaion
of a program called com0com.
Before we can install and configure com0com or VSP Manager, we need to check the computer to see what COM ports have been assigned over the life
of the computer. Every time a device is plugged into a USB port, Windows assigns it a COM port. If the same device has been inserted in a
variety of USB ports, Windows will have assigned a different COM port for each insertion. This can result in many assigned, but unused COM
ports that will interfere with the configuration of com0com. Multiply all the different USB devices ever plugged in by the number of possible
USB ports and you get an idea of the magnatude of the problem.
So, take a look at the the ports Windows has assigned on your computer and remove those that are not necessary using this Windows XP information.
- Windows 7 users, you can use the same information as for XP (above) except that when you right click Computer and select Properties a system window
will open where you select "Advanced system settings".
- It may be necessary to run the Device Manager mentioned in the linked instructions with administrator priveleges. To do so in Windows 7 or Vista,
just use Windows explorer to navigate to the c:\windows\system32 directory then right click devmgmt.msc and select "Run as administrator".
Here's an example of a Win 7 system where the same device has been assigned four COM ports, only one of which is in use. Note the three light gray icons,
COM5, COM6 and COM7, which should be removed.
OK now that you've removed the COM ports Windows assigned, but is not using, we can download and install com0com or VSP Manager.
For com0com (requires Microsoft .NET Framework 3.5 to use GUI)
Test your computer and sound card -
Windows 32-bit users, download and install the latest version (22.214.171.124) at Com0Com Virtual Com Port Emulator
Windows 64-bit users should use the signed version 126.96.36.199 (top one) .
To install and comfigure com0com use these instructions (disregard version information, I will write new instructions as time permits).
Many users, including SignaLink USB users, will need only Virtual Com Port Pair 6/16.
For VSP Manager (requires Microsoft .NET Framework 3.5 to use GUI)
Note: Make sure you enable buffer overrun for the port pair that commnicates between BlockTerm and the DMT.
Flex radio users should define a Virtual Com Port for PTT. I use Virtual Com Port Pair 8/18.
I also use Virtual Com Port Par 7/17 for Flex Radio CAT control. You likely won't need this pair.
This is what my com0com looks like:
Installing MS-Data Modem Terminal (MS-DMT) -
- Download and run DPC Latency Checker.
- DPC Latency Test (Download and rename dpclat.dld / dpclat.exe).
Let it run for 15-20 minutes and observe the absolute maximum number. If you see a high absolute
maximim and current latency is low, then you have a program or device that is consuming too much processor
time. My Flex radio computer runs a maximum of about 210 uS.
- Download and run Check Sound Card Offsets.
- Check Sound Card Offsets (CheckSR) v1.1 (Download and rename CheckSR1.1.dld / CheckSR1.1.exe).
Press Start and let it run for 15-20 minutes then press the Stop button and observe the difference ppm number.
For best results the difference must be below 20 ppm
NEW 4/29/13 - BlockTerm versions later than 4.0 require Modem MS-DMT v1.00 Build 188.8.131.52 or later.
Installing and configuring BlockTerm -
NOTE: For best results you should install it in at c:\MS-DMT.
NEW 10/25/13 - The links below install V1.00B Build 184.108.40.206.
If you have never installed an earlier DMT, download and install the full package here
http://w3jjj.com/blockterm/MSDMT32v100B1002_FI.ZIP then continue with this page.
If you have already installed an earlier DMT, download and install the partial package here
http://w3jjj.com/blockterm/MSDMT32v100B1002_PI.ZIP then continue with this page.
Enter the lower number of the Virtual Com Port Pair you have defined in the Data Port (in this case 6).
IMPORTANT! - M110A DMT cannot use any port higher than COM16 for either DATA PORT or CAT COM PORT.
Enter the port and data rate you use for PTT control in the CAT Com Port (SignaLink USB users should enter 0).
NOTE: If the DMT reports the unavailability of dalog or owlog, your installation did not create the directories.
You should use Windows Explorer to navigate to the M110A root directory and add a dalog and owlog directory.
To find the M110A root directory right click the M110A DMT icon and select Properties.
The DMT should look like this:
Left click the PSCDM button and select your sound input and output devices:
This one is for the SignaLink USB
This one is for the Flex radio
Requires Microsoft .NET 4 framework, available at this link.
Download and install Block Terminal V6.0.
Configure your BlockTerm as shown below.
Type sonmething into the Transmit Data box and press "Send Text". The data you typed will be sent through com0com to the DMT where it will be
The Help menu for BlockTerm is being developed as time permits. Please check often for changes.
Flex Radio Users, you should review the information at this link for best results with M110A.
formatted for M110A and transmitted.
Use the File>Open menu to load a small text file. Once loaded, set the Transmit Data Block Size to 256 then press "Send Block". The data will
be broken into several blocks and sent as individual messages with a delay equal to the Tx delay between blocks (sec.) setting.
This is what the LED's in BlockTerm indicate:
When BlockTerm first starts, both the DATA and PTT LED's are red.
Select the higher port number of your virtual Com port pair and set the speed to 57600, then press "Connect".
Set the DATA PORT on the DMT to the lower port mumber of the virtual Com port pair and match the speed setting.
When BlockTerm is connected to one port of the Virtual COM port pair both the DATA and PTT LED's will be green.
This does not mean BlockTerm can communicate with the Data Modem Terminal (DMT), simply that it is connected to the selected COM port.
If bloth LED's are not green when connected, check your virtual serial port software to ensure the ports are properly configured.
When DMT receives data from BlockTerm it raises the DTR pin on the DATA PORT to let BlockTerm know it's transmitting.
BlockTerm mointors DCD (the receive side of DTR) and turns the PTT LED yellow to let the operator know DMT is transmitting.
If the PTT LED does not change to yellow when the DMT transmits check your virtual serial port software or your modem cable.
The BlockTerm DATA LED is yellow while data is being processed.
When all data has been sent, both LED's will change to green. This is the normal condition for receive.