Ee Ff

fab/e 2, Hex codes for letters and punctuation.

Equipment Required

The Cosmac microcomputer constructed around the CDP1802CD CPU is used with 256 bytes of RAM of which 105 bytes are used for the main program, the rest being used for storage of the messages, Program timing assumes a clock frequency of 1 Ml lzr but it is easily adapted for other clock frequencies Other hardware that you will need is shown in Fig, 1. This includes some ICs to interface the computer and hand key to the transmitter and a sidetone oscillator.

How the Program Works

The byte stored in M(00Q4) is selected initially by the operator from Table 1. This byte sets the length of a dot and hence sets the speed of the code I he program triples this to get a number that will represent the length of a dash; this is stored in R6.0. Four times the dot byte represents a word space, and this byte is

Q LINE FflQfo &

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