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Parallel interface

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The parallel port data options control which port address is used and what electrical conditions are used to signify high and low logic levels. You can toggle individual port data bits or specify a decimal number for these logic levels. The port address is input as a decimal number although a hexadecimal value is also displayed by NuMorse. By default, the printer parallel port is selected with 0 and 255 for logic low and high. The enabled check box acts as a master switch for this feature. This feature works under Windows 2000 and Windows XP. It has not been tested under Windows Vista.

 

Note that the port address defaults to the printer port which has built-in hardware decoding on most PCs. If your PC uses a USB printer then you will need a USB to parallel interface adapter to use this feature You will also need extra port address decoding hardware if you intend to use a different port address than the printer address.

 

A representation of the logical levels of bits 0-7 of the selected port is shown together with the corresponding value (in decimal) that NuMorse will send to the port during tone on and tone off periods. You may adjust the values by editing the decimal value or you may toggle the logical levels by clicking on the bit map.

 

parallelinterfaceb1

 

Be aware that the bit map shown in NuMorse  refers to logical bit numbers NOT physical pinouts. See the diagram below for the correspondence between port data bits and physical pinouts.

 

A figure of 255 for High would cause all the port bits to be set to logic HIGH during the time that a dot or dash were being sent. A figure of 0 for low would set all the port bits to logic LOW during spaces. Setting High to 254 would result in the port bits all staying logic HIGH except for bit 0. The permanently HIGH bits could, with care, be used to power an external device such as a code practice oscillator while the remaining bit would toggle up and down to switch the oscillator on/off.

 

A simple circuit to operate a tone oscillator from a hardware port data.parallelinterfaceb2

 

Data pinouts.

 

Here are the data pinout details for a Centronics parallel printer port, this view is looking into the rear of the PC.

 

parallelinterfaceb3

 

Pin       Signal

2          Bit 0

3          Bit 1

4          Bit 2

5          Bit 3

6          Bit 4

7          Bit 5

8          Bit 6

9          Bit 7

33        GND